An investigation is under way after a row of terraced houses was destroyed by fire in Burnley.
The blaze broke out at the houses, which were still under construction, in Accrington Road on Wednesday night.
Lancashire fire investigators are trying to establish whether anyone was inside when the fire started.
One local resident said children sometimes played in the houses and that they had also been used by squatters.
Elizabeth Upton, who lives on Accrington Road, said: "This is something we have been waiting to happen, because the houses have been empty for so long.
"The kids have been going in and just playing, you can hear them, and we've had squatters going in there.
"All that was inside was wood. They'd put all the framework in there, the floors and the staircases, and that was it."
About 50 firefighters were called to the scene and a number of properties surrounding the area were evacuated while crews worked to douse the flames.
Fire crews had brought the blaze under control by 2100 BST but two engines remained at the scene damping down.
Nelson station manager Barry Hornsby said: "The structure has collapsed but there are still parts of it that are very unsafe.
"There still will be hotspots burning in the morning so we'll be damping down for some considerable time."
Several roads, including Old Accrington Road and Blannel Street, were closed by police during the incident and some diversions remain in place.