Police are treating a blaze at Total Recycling Services in Darlington as suspicious.
The two-storey office block at the facility was on fire when emergency services arrived at 11:20pm on Saturday 23 June and remained until 4am attempting to put out the blaze.
Last month, Total Recycling Services suffered another blow when £50,000 of equipment was stolen.
County Durham and Darlington Fire and Rescue Service group manager John Robson said: “There was substantial damage to the building. Our main objective was to make sure the building was safe to enter in order to extinguish the fire.”
He added that the firefighters encountered a number of separate fires at the scene and it wasn’t clear if this was because the fire had spread, or is there was more than one source of fire. He is hoping the investigation will reveal why this occurred.