Firefighters are continuing to battle a blaze at a site where Miller Construction is building a £16m police training facility.
The fire at the firearms training centre in Valley Road in Portishead, Bristol was spotted by a passing police officer in the early hours of Tuesday morning.
Avon Fire & Rescue Service said they had remained on the scene overnight and were still tackling pockets of fire so were likely to be on site for much of today.
Avon & Somerset Police assistant chief constable, Dave Hayler, said the Black Rock Quarry training centre was badly damaged. The facility is shared by the of Avon and Somerset, Gloucestershire and Wiltshire police forces.
He said: “The damage is extensive and we’ll be working closely with fire investigators and our own forensic teams to understand what happened to cause such a large fire. The fire service will be on site for some days to come until they’re absolutely satisfied that any danger of the fire relighting is exhausted.”
A statement from Avon Fire & Rescue Service said: “The investigation into the cause of the fire will begin once the fire is completely extinguished and it is deemed safe to enter the building.”
The £16m project is part of a PFI deal which includes two custody and crime investigation centres and an operations base in Somerset being developed by the Blue Light Partnership made up of Bilfinger Project Investments and Miller Construction.
Construction work on the firearms centre was originally meant to take 50 weeks with 70 per cent of sub-contracts going to local suppliers.
A spokesman for Miller Construction said only the emergency services were commenting on the incident.