Officers were alerted to the incidents in the Layerthorpe area of York by the fire and rescue service in the early hours of Monday morning.

The six vans belonging to Carillion Energy Services were set alight at a compound on Ebor Industrial Estate – four of the vans were completely destroyed.

Residents reported hearing explosions in the area, which police believe were the diesel tanks catching fire.

Officers are treating the fires as suspicious and are appealing for anyone who can help the investigation to get in touch.

Detective Constable Sinead McConigley, of York CID, said: “We believe that these fires were a deliberate act and are appealing for the public to help us identify who is responsible.

“I urge anyone who saw any suspicious people or vehicles in the area at the time of the incidents to contact the police or Crimestoppers immediately.

“Arson is a serious crime which can be extremely dangerous. Fortunately, nobody was hurt on this occasion but fires can be lethal and incidents like these cannot be tolerated.”

Anyone who can help the police with their enquiries is urged to contact PC Sinead McConigley, of York CID, on 0845 60 60 24 7, quoting reference number 12110137609.