Owner and managing director Henry Carver praised the "huge dedication" of staff since the fire, which was caused by "a malfunctioning flue pipe".

BBC: Carvers fire, Wolverhampton

During a routine run in 1986 a few days after the Chernobyl fire, one of the pebbles became lodged in a pipe feeding the fuel to the reactor.

ECONOMIST: Prospects for a new type of nuclear reactor look mixed

Authorities announced the criminal investigation last Friday, the same day investigators said a paramedic who responded to the fire was arrested on suspicion of possession of a destructive device after investigators allegedly found materials to make a pipe bomb at his home.

CNN: Cause of catastrophic Texas explosions remains mystery