Investigations into a fire at the new police firearms training centre in Portishead cannot begin until the fire is fully extinguished and structural engineers confirm that it is safe to enter the building.
Crews were still damping down at the scene in Black Rock Quarry last nigh and specialist equipment has been brought in to help gain access to the centre.
The cause is currently being treated as unexplained - despite claims from an anarchist group that they started the fire on Monday night.
Valley Road is closed in both directions due to the fire between Down Road and B3124. Police advice is to use the Coast Road or Portishead High Street. The closure is likely to be ongoing for some time. Initial reports suggest closures could be in place until at least Friday.
Avon and Somerset Police have confirmed, Special Branch are investigating claims on a Bristol website that a group was responsible for a fire at a new regional Police training centre in Portishead on Monday.
A Bristol website has posted claims by a group purporting to call themselves Angry Foxes Cell that it started the fire at the new regional Police training centre in Portishead which is under construction.
Avon and Somerset Police said its investigation is ongoing and Valley Road remains closed while Fire Investigators look into the cause of the blaze.