POLICE have made no arrests and believe that 19-year-old Dzhohkar is no longer in Watertown, but still hiding somewhere in Massachusetts. re combing homes in a Boston suburb as part of a frantic search for a suspect in Monday's marathon bombing after a bloody night of shooting saw a second suspect and a police officer killed.
US authorities are "committed" to apprehending the most wanted man in America, 19-year-old Dzhohkar Tsarnaev, whom they believe is still in hiding in Massachusetts.
The Amtrak train service from Massachusetts to New York and New Hampshire are still suspended, while the governor has lifted the stay indoors request and public transport on the MTBA has resumed as normal.
At the latest Boston press conference, Colonel Timothy Alben of the state police said: "We remain committed to this.We do not have an apprehension of our suspect this afternoon, but we will have one.
"I want the neigbourhood here in Watertown to know that we went through about 20 streets, going door to dootrwith our tactical teams to ensure everyone is safe in their homes. We’ve also followed a number of leads this afternoon taking us to various places in Eastern Massachsetts. None of those leads have been fruitful at this point.
"There is much more to be done, we still have ballistics and forensics work to be applied."
The two suspects killed a university police officer, injured a transport officer in a firefight and threw explosives at police during a getaway attempt in the early hours of the morning across the towns of Cambridge and Watertown, west of the city still recovering from this week's terrorist attack that killed three people and left over 150 injured.
The identity of the MIT police officer has been released. He is Sean Collier, 26, of Somerville.
The latest images show heavily armed police with guns drawn surrounding a house at the corner of Willow and Quimby.
A man and a woman have been taken into custody, though they are not thought to be suspects yet, reports CBS.
Police said this afternoon they were carrying out at least one controlled explosion on Norfolk Street, in Cambridge, not far from where the bombers reportedly share a home.
The Boston Globe is reporting that that the FBI believe that the missing suspect may be driving a green, four-door Honda Civic.
The FBI are understood to have been in contact with the suspect's aunt in Toronto and sister in New Jersey.
The FBI removed a computer from the New Jersey home of the sister of the bombing suspects.
Police in West New York said the woman is cooperating in the investigation, but they did not immediately release her name. They have cordoned off the three-story brick building across the Hudson River from New York City.
The woman, speaking earlier through a crack in the door, said she is sorry for the families who lost loved ones.
She said she does not know what got into her brothers. At the same time, she said she does not know if it is true that her brothers were responsible.
The missing suspect has been identified as 19-year-old Dzhokhar Tsarnaev from Cambridge, Massachusets. National security officials have confirmed that the two suspects are brothers; their uncle has confirmed the suspect killed by police was Tamerlan Tsarnaev, 26.
Ruslan Tsarni of Montgomery Village, Maryland, is reported as saying that the men lived together near Boston and have been in the United States for about a decade. They travelled here together from a Russian region near Chechnya.
The brothers' father Anzor Tsarnaev is reported to have said in a a telephone call from Russia that his son Tamerlan was "a true angel" and that he was a second-year medical student in the US.
Dzhokhar Tsarnaev appears to been educated at at a Cambridge high school before receiving a scholarship to pursue higher education in 2011. His name appears on a list of 45 recipients of the Cambridge City Scholarship, handed to students from Cambridge Rindge and Latin School.
Dzhokhar was born in Kyrgyzstan and has a Massachusetts driver's license, according to officials cited by NBC News. Tamerlan is believed to have been born in Russia.
Boston police commissioner Ed Davis confirmed that Dzhokhar is still at large in Watertown, a town about 6 miles north-west of Boston. Swat teams could be seen approaching houses in Watertown as the sun rose this morning as they conducted a house-to-house search across a 20-block perimeter.
The Boston Globe reports officers dragging a handcuffed woman out of the address the suspects were believed to be living in.
The whole of Boston is under a 'shelter in place' order. Everyone has been asked to stay indoors.
Mr Davis earlier described Dzhokhar Tsarnaev as the 'white hat suspect,' referring to a man seen in video footage released by the FBI late last night of people they believed to be involved in the marathon bombing.
In a news conference, Mr Davis said: "We believe this to be a terrorist. We believe this to be a man who has come here to kill people. We need to get him in custody."
Police say Dzhokhar Tsarnaev is believed to be wearing a grey hooded sweatshirt. He is white with dark hair and appears to be in his twenties.
Colonel Timothy Alben, superintendent of Massachusetts State Police said: "We believe these are the same individuals that were responsible for the bombing on Monday of the Boston marathon. We believe they are responsible for the death of an MIT police officer and the shooting of an MBTA officer."
Locals are being warned to be extra vigilant after reports of a suspicious device by staff at the Massachusetts Institute of Technology (MIT) in Cambridge. The area is in lock-down, as authorities order businesses not to open and all traffic to be stopped while the operation continues.
The sequence of events began late last night with the armed robbery of a 7-11 in Cambridge, followed by reports of loud shooting on the campus of the Massachusetts Institute of Technology (MIT). A campus police officer was shot after investigating a disturbance in the area and later died in hospital.
Minutes later a black Mercedes was carjacked from Kendall Square, close to the shootout, leading police on a chase through Watertown.
The chase led officers through a residential neighbourhood, where a shootout ensued between officers and the two suspects.
Police confirmed that explosive devices were thrown at officers from the vehicle the suspects were traveling in.
In the ensuing firefight, one suspect was shot while the other managed to flee.
A transport police officer, identified as 33-year-old Richard Donohue Jnr, was also hit and is currently in surgery at a Cambridge hospital.
Pictures posted on Twitter by witnesses in the residential area showed a man with a large backpack standing off with police.
The injured suspect was later pronounced dead in hospital.
Officials at Beth Israel Hospital in Boston said a man was brought in heavily guarded by police and was already under "traumatic arrest". Staff said that the man's injuries were consistent with multiple gunshot wounds and a blast of some sort, possibly from an explosive device.
Dr Richard Wolfe, chief of emergency medicine at the hospital, said that the man's injuries were "more than just gunshot wounds".
Hospital staff refused to give details about the man's identity.
Watertown was in lockdown this morning, with hundreds, and possibly thousands, of police, FBI, bomb squad and national guard personnel combing the town's streets for the second Boston marathon bomb suspect. At the eastern end, a police cordon was up around the Coolidge Square area.
Kris Hagopian lives inside the exclusion zone. Last night, he was at his mother's home just beyond the cordon when he saw the news break on TV. His wife and children are still inside the closed-off area, in their home, as is his sister and her family.
On Monday, Mr Hagopian says, standing outside the 7-11 just beyond the cordon, he was near the marathon finish line on Boston's Boylston Sreet. “Now, look, its come to my town,” he said.
On his phone, he showed the texts messages he'd sent to his son, asking his family to bolt the doors and windows.
“This is a small community, mostly Armenians and Greeks. Everyone knows everyone by name,” he said, pointing in the direction of the exclusion zone.
“I own a liquor store in there,” he said, waiting beyond the police line at 6 am.
Massachusetts State Police warned people in the suburb to stay inside as they conduct a door-to-door, street-by-street search.
All public transport in Boston has been suspended and all classes at MIT cancelled. Harvard University, also in Cambridge, will also be closed.
Federal officials last night had significantly widened the investigation into the bombing by releasing photos and a video showing the men near the site of the explosions.
Richard DesLauriers, the special agent in charge of the Federal Bureau of Investigation's Boston office, said he considered the two suspects “armed and extremely dangerous” and asked the public to pass on any tips to law enforcement officials.
The first suspect was observed wearing a black cap, while the second one was seen wearing a white cap, Mr DesLauriers said. Both appeared to be carrying bags on their backs. According to the FBI, the second suspect placed his bag at the site of the second of the two blasts that struck the marathon on Monday.
The explosions killed three people and wounded more than 170 near the marathon's finish line on Boston's Boylston Street. The youngest fatality was 8-year old Martin Richard from the nearby community of Dorchester. 29-year old Kyrstle Campbell and 23-year old Lu Lingzi, a Boston University graduate student from China, were also killed by the blasts.
“Today we are enlisting the public's help to identify the two suspects... Somebody out there knows these individuals,” Mr DesLauriers said.
The developments came just hours after President Obama and first lady Michelle Obama attended a special service for the victims at Boston's Cathedral of the Holy Cross.
Nikhil Kumar and Caitlin McBride
View Larger Map