THE FBI was alerted by Russia's security services to serious concerns about one of the Boston bomb suspects as recently as November, it has been claimed.
As the agency was accused of "dropping the ball" over the case, NBC News reported that Tamerlan Tsarnaev had been seen making six visits to a known Islamic militant in a mosque in the Russian republic of Dagestan.
The visits happened during a six-month trip that he made to the city of Makhachkala to see his family, NBC said.
According to a local police official, a file on him was handed to the FBI, along with a request for more information. The FBI failed to reply.
The agency has already admitted that it interviewed Tamerlan Tsarnaev in 2011 after Russia raised concerns that he was becoming a follower of radical Islam, but found nothing "derogatory" against him and did not pursue the case.
The 26 year-old, who allegedly orchestrated last Monday's bombings with his younger brother Dzhokhar, was killed in the early hours of Friday in a shoot-out with police. It took place just hours after detectives released images of the pair to the public.
In a further twist, Channel 4 News claimed yesterday that Tamerlan had phoned home after the bombings and told his mother that the FBI had already called him to accuse him of being responsible.
According to the report, he replied to the accusations by saying: "That's your problem."
The FBI declined to comment on either claim. If either is confirmed, it will add significant weight to the growing chorus of criticism of the FBI.
Yesterday senior members of Congress accused the bureau of repeatedly "dropping the ball".
Michael McCaul, the chairman of the House homeland security committee, said the FBI must explain why it failed to keep track of Tsarnaev after the 2011 interview, particularly after he visited Dagestan, a known centre of Islamist militancy and training facilities.
"If he was on the radar and they let him go, if he was on the Russians' radar, why wasn't a flag put on him, some sort of customs flag"" Mr McCaul asked on CNN.
"One of the first things he does [upon his return] is puts up a YouTube website throwing out a lot of jihadist rhetoric. Clearly something happened, in my judgment, in that six-month timeframe – he radicalised at some point in time," Mr McCaul added. "Where was that and how did that happen?"
The 'New York Times' reported that a "hold" had been placed on his citizenship request by the Department of Homeland Security after routine background checks discovered the FBI's former interest in him.
The FBI has not explained why it did not immediately retrieve the Tsarnaev file after the Boston bombs went off - an event that should have triggered routine checks on those suspected of involvement with Islamist militant groups.
Even when three days later, the FBI identified the bombers, it failed to cross-reference photographs with the man whose picture was on file. When asked why the file had been overlooked, the FBI said it would not comment on "operational matters".
Senior politicians openly questioned the competence of the FBI.
Senator Lindsey Graham warned: "It's people like this that you don't want to let out of your sight, and this was a mistake.
"Either our laws are insufficient or the FBI failed, but we're at war with radical Islamists and we need to up our game." (© Daily Telegraph, London)
Tight security at London Marathon