A parking garage with 200 cars was set on fire overnight in the Swedish town of Marsta, north of Stockholm.
"The roof has collapsed and the building can no longer be saved," a spokesman for rescue workers told the Swedish news agency TT.
Firefighting efforts were very difficult, he said, describing it as "like being in a blast furnace."
Because of the heat, firefighters could not get close enough, he said.
The fire was said to be under control and no injuries were reported. The cause of the fire is being investigated.