An anarchist group has claimed it started a fire which ripped through a police firearms training centre being built in Somerset.
A passing officer spotted the blaze at the Black Rock centre in Portishead in the early hours of Tuesday.
In a post on the Bristol Indymedia website, the group, called "Angry Foxes Cell", says it "used accelerant to burn the major electrical cables".
Police said it is too early to decide "cause or responsibility".
A spokesman said the group's claims were "one of the lines of enquiry" and a forensic team will be investigating the incident.
He said he wanted to stress that as the facility was still under construction it did not contain ammunition or anything that posed any danger to the public.
Avon and Somerset PCC Sue Mountstevens described the fire as "devastating".
She apologised to the local community for any inconvenience caused by the fire and while the site is being made safe.
'Rebellion against slaughter'
The group said in the post that its members targeted the construction site on Monday night, leaving it with "flames licking high".
Angry Foxes Cell said it "puts smiles on our faces to realise how easy it was" to target the building.
The statement claimed the group also slashed tyres and poured paint stripper on two vehicles in Bristol - one belonging to the security company G4S and the other to GEOAmey, a firm that transports prisoners.
The post concludes by saying the "night of action coincides with the announced start of the planned cull of wild badgers in the south-west of England".
"Through attempting to facilitate the cull and stop resistance the police shore up the interests of agricultural industry and the land-owning classes.
"We hope this will be one of many rebellions against this slaughter."
The final sentence says: "The struggle will continue until all are wild and free."
Avon and Somerset Police said no-one had been arrested in connection with the badger cull in west Somerset.
A G4S spokesman confirmed one of its vehicles had been damaged, while GEOAmey said none of its fleet in Bristol had been vandalised.
A fire service spokeswoman said the cause of the blaze was not yet known.
"Firefighters are likely to be there for some time checking for any hot spots to make sure the blaze doesn't reignite," she said.
"Once the building is secure an investigation into the circumstances of the fire will take place."
Valley Road remains closed and drivers are being advised to take alternative routes. Firefighters are expected to be on site for several days.
The centre, which is being built at Black Rock Quarry, is to be used by the Avon and Somerset, Gloucestershire and Wiltshire forces.
The facility, which will contain two indoor firing ranges and classrooms, is due to open in January.
It is part of a Private Finance Initiative (PFI) deal, worth more than £100m, which will also see police stations and other operational facilities built in Patchway, Keynsham and Bridgwater.
Bristol Indymedia is a volunteer-run open-access news website which is part of the global Indymedia movement which covers "grassroots, non-commercial news".