A probe is under way after a massive explosion rocked a Perthshire housing estate.
Dozens of neighbouring homes were evacuated following the blast at around 4.30am.
Four teams of firefighters spent about three hours battling the inferno, while police led the evacuation. All the damaged properties were empty at the time and no one was injured.
A joint investigation involving police, fire chiefs and housing developer Stewart Milne has been launched.
The company’s managing director John Low said: “The homes which have been affected by the fire were nearing completion, but had not yet been handed over to our customer and therefore not occupied.
“Thankfully no one has been hurt and we’d like to thank the fire service for their prompt response.”
He added: “Our preliminary findings reveal that the fire probably started in a welfare unit, close to the building site.
“This is a container where site workers are able to change and dry their clothes.
“We are working closely with the police and the fire brigade to investigate the cause. Meanwhile, our management is on site ensuring everything is being made safe and secure.”
Residents were offered temporary accommodation at the nearby Blairgowrie Recreation Centre.
Neighbour Paul Black said: “It was about 4.30am. We were woken up with a loud bang that made the whole place shake. I thought a car had hit the side of the building.
“I looked out the window and could see a lot of people out on the street. When we went outside, we could see the shed was ablaze.
“The flames were just about reaching the houses when we came out.”
Surrounding homes were evacuated by police, although most of the residents were already outdoors, watching the action, in their pyjamas.
Paul’s wife April said: “It was about an hour-and-a-half before we were allowed back into our homes.
“Everyone was out on the street. People who hadn’t been evacuated were offering us teas and coffees, so there was a nice bit of community spirit.”
Speaking at the scene, Blairgowrie-based Watch Manager Chris Smith said: “We were mobilised at 4.30am to reports of a fire in a shed at Blackthorn Place. Four units from Blairgowrie, Alyth and Coupar Angus attended.
“The cabin was well ablaze when we arrived and the fire spread to the timber frames on the house roof next door.”
Crews used hose reel jets to bring the blaze under control.
Local SNP councillor Tom McEwan praised emergency services for their swift response and said the council’s housing department went door-to-door to ensure residents’ concerns were addressed.
“It is good to hear residents affected were promptly evacuated and emergency accommodation at Blairgowrie Recreation Centre was provided.”
Conservative councillor Bob Brawn added: “This must have been a very scary experience for residents, but thankfully no one was hurt.”
A Police Scotland spokesman said: “The fire was within a building site and nearby homes were evacuated purely as a precaution.
“Inquiries into the circumstances are ongoing.”
