Two blocks of flats were evacuated and a woman was arrested on suspicion of arson after a fire, believed to be caused by a disposable barbecue, in Calne on Monday evening.
Police officers were on routine patrol in Harrier Close at around 8.30pm, when they spotted a brick bin area, attached to a block of flats, on fire.
The fire brigade were called and, while they were en route, officers evacuated both the adjoining block of flats and the adjacent buildings, including Tesco Express.
As the evacuation was taking place, the bin area, which is a small brick building joined on to the main block of flats, collapsed, sending debris into the road.
Four fire engines arrived at the scene, two from Chippenham, one from Calne and one from Melksham, and the blaze was quickly under control.
After making enquiries, police arrested a woman on suspicion of arson, without intent. It is thought a group of people had been holding a barbecue on Monday afternoon and disposable devices had been disposed of in the bins, possibly causing the fire.
Sergeant Phil Connor, of Calne Police, said: "One female has been arrested on suspicion of arson, without intent. She has been taken to Melksham Police Station for questioning.
"We have a list of witnesses to the incident but would appeal to anyone who saw any of the events leading up to the fire to call Wiltshire Police on 101."