Arson was the cause of a Boxing Day blaze in Berkhamsted High Street, police have announced.
Firemen have been investigating the garage fire opposite the Total petrol station since it happened.
At the time, watch commander Dick Lawrence said the fire - just yards from people’s homes - could have caused a major explosion.
The building, full of gas cylinders, was severe damaged.
Police spokesman Sarah Spence said: “What we believe may have happened is that the offender(s) have smashed a window at the rear of the premises to gain entry.
“Then they set a fire inside before leaving the way they came in.”
Witnesses of the event, which took place at about 5.30pm, should phone police on 0845 33 00 333 and quote crime reference number D2/11/23.