The PSNI believe a fire in Coleraine, County Londonderry, last Sunday may have been started deliberately.
The fire spread from an oil tank to a house on the Ballycastle Road at about 04:00 GMT.
A man, a woman and a small child were taken to hospital and treated for smoke inhalation .
The occupants and neighbours were moved from their homes while fire crews tackled the blaze.
Substantial damage was caused to the house.
PSNI Detective Sergeant Kelly Gallagher said: “Following enquiries, it is believed that this fire may have been started deliberately.
“I would therefore appeal to anyone who may have seen any suspicious activity in the area between the hours of 2am and 4am, or anyone who knows anything about this incident, to contact detectives at Coleraine Police Station.”