A pregnant woman and a man had to jump from the upstairs window of a house that went on fire in the early hours of yesterday morning.
A four-year-old girl was taken to safety from the upstairs window too, while two other adults escaped from the ground floor as the blaze consumed the downstairs.
A Garda spokesperson said an investigation was under way and it was believed a petrol bomb was the source of the blaze in the two-storey end-of-terrace house in Clontygora Court, Dundalk, Co Louth, which began at around 3.35am.
Gardaí have set up an incident room at Dundalk garda station and have appealed for anyone who witnessed anything or who has information on the incident to contact them.
The woman whose house was targeted in the attack told of how she desperately tried to rescue her family.
Speaking to LMFM, the woman said: "I ran down the stairs and I saw the fire in the sitting room so I opened the front door to leave the smoke out to go back up and get my granddaughter out cos she's only four.
"When I got back upstairs you couldn't see your hand in front of you. So I tried to get my daughter-in-law down the stairs because she's seven-and-a-half months pregnant."
She said she got her husband out of the house and returned upstairs to help her daughter-in-law but could not get her out.
"I opened all the windows in the house and they had to jump from the top bedroom window. A seven-and-a-half months pregnant woman had to jump out a window," she said.
Louth Sinn Féin TD Ruairí O'Murchú, who visited the scene, said a man and his family "were trapped in the room upstairs, they had to open the back window and jump out".
The man and woman are believed to have broken their ankles.
Their four-year-old child is understood to have been handed down from the window upstairs to a member of the public who responded after hearing screaming.
"It is very lucky we are not talking about fatalities or serious, serious injuries.
"This is incredibly serious. It is absolutely shocking what you see in that house and it is pure luck we are not looking at coffins," said Mr O'Murchú.
He added that he was thankful that neighbours were so vigilant.
One member of the public is understood to have made a number of attempts to get up the stairs on hearing a child and a pregnant woman were there. The person was beaten back by smoke and flames and then went to assist in helping the child to be handed to safety from the back upstairs window.
Two tenders from Dundalk Fire and Rescue Service responded to the call.
Assistant Chief Fire Officer Colm Lambe said they were notified at 3.40am and, when the crews arrived: "It was well ablaze, the sitting room along with the kitchen. They got the fire contained to that area so it did not spread upstairs."
He also confirmed that two adults had jumped from the top window.
All of the five occupants remained in hospital yesterday and some were believed to be in intensive care as they received treatment for smoke inhalation.
The house was severely damaged in the blaze, with the ground floor practically gutted and the first floor blackened with smoke.
The heat from the fire shattered glass panes on both levels and melted the guttering which rained molten plastic down to the ground.
The living room and dining room suffered the worst damage, where the furniture and doors were charred to soot.