PART of the floor of a child's bedroom is believed to have collapsed after arsonists set rubbish and furniture alight in a covered alleyway.
The blaze was started in the early hours of Friday morning on Victoria Street in Lurgan, Co Armagh, with Fire Service alerted shortly after 5am.
The fire spread and caused damage to the back of two terraced houses.
Police said firefighters' prompt response had prevented the entire row of houses going up in flames - three appliances were dispatched to the scene.
A woman and two children in the house closest to the fire were able to get out by themselves. No-one was injured although it is believed that part of the floor of a child's bedroom collapsed in one of the houses which sustained scorch damage.
The PSNI confirmed it had been started "deliberately".
A Fire Service spokesman said: "Firefighters using a hosereel jet dealt with a large quantity of rubbish and furniture on fire in an alleyway in the area. The fire spread and caused damage to the rear of two terraced properties in the area.
"Northern Ireland Fire & Rescue Service finished at the scene at 6.11am and the fire is being treated as deliberate."
The PSNI Craigavon Facebook page carries an appeal for the public's help.
"There is no doubt this was deliberate, started in an alleyway between houses, and we are very keen to get speaking to a male described as wearing blue jeans and a dark jacket, possibly holding a carry-out, in the area of William Street and Victoria Street around 5am this morning," it said.
"If you saw or heard anything, or hear of anyone smelling of smoke and guilt, please call us on 101, quoting incident number 164 of 06/05/16. If you would rather speak anonymously, call Crimestoppers on 0800 555 111.
"Thankfully, nobody was hurt during this incident. Neighbours looked out for each other and woke pretty much the whole street to make sure everyone was safe.
"Our NIFRS colleagues did an epic job making sure it didn't spread further. Without doubt we would be talking about serious injuries or worse if it weren't for the actions of these folk."
