Fire officials have cited "spontaneous combustion" in a Friday fire that sent smoke across the Bay.

The fire happened about 5 p.m. at Trademark Metals Recycling Facility on Port Sutton Road in Tampa.

Crews needed several hours to bring the two-alarm blaze under control.

"The process of spontaneous combustion typically happens due to a buildup of heat within the pile. This is caused by the materials oxidizing, and the heat from that chemical reaction being trapped," Hillsborough County Fire Rescue said in a news release.

No injuries were reported.