Witnesses heard and felt powerful explosions before a fire at a downtown Los Angeles building Tuesday that sent thick smoke over the Skid Row area.

The fire and explosions were reported at about 2 p.m. in the 600 block of South Kohler Street. Firefighters protected an adjacent three-story apartment building from the fire, which sent plumes of thick smoke over downtown LA and the Skid Row area.

“Bystanders stated there were explosions, describing it as multiple explosions… with balls of fire rising into the air,” said LAFD Capt. Erik Scott.

Scott said the building was vacant, but there appeared to be pressurized cylinders inside. It was not immediately clear for what the cylinders were being used.

Firefighters on at least three ladder trucks were spraying water on the building, the roof of which appeared to have collapsed.

There were no reports of injuries. Details about a cause and the type of business were not immediately available.