Capricorn Motors, a garage in Bath, has burnt to the ground, destroying the building, workshop and three clients’ cars.
The fire has caused an estimated £250,000 of damage.
The blaze at Capricorn Motors, on Newbridge Road, began in the early hours of yesterday morning and is being treated as suspicious. Manager, Marcus Harvey, was woken by police at 5am and rushed to the scene.
Several cars, which were parked on the forecourt, escaped the blaze but four were partly melted because of the heat.
"I was not expecting it to be so bad," said Harvey.
"We don't yet know what caused it and have had police and fire investigators round. The problem is that the keys for the cars are melted so we can't move them and some of them are sold.
"I have got a lot to sort out now and will probably board up the building and maybe operate from a temporary one."
Harvey, who has worked at the garage for more than 18 years, said that much of the business paperwork was at the company's other garage, Rodden Road Cars in Frome.
Police, who were called to the scene of the blaze just before 2am yesterday, estimated the cost of the damage to be around £250,000.
Firecrews faced an extra challenge in tackling the fire because there were flammable chemical cylinders inside the building. The acetylene cylinders, which are used during welding, had to be cooled to stop them from exploding.
A spokeswoman from Avon Fire and Rescue said last night: "We went back to the scene on Wednesday morning to make sure the fire was properly out.
"Our investigators have also been there today to try to establish the cause of the fire.
"At the moment we are treating it as suspicious but this will be confirmed once the investigation is finished."
An Avon and Somerset police spokesman added: "We have been working closely with the fire service to investigate the fire. We are treating the fire as suspicious."