OAKLAND (CBS SF) — A massive 3-alarm fire erupted inside an Oakland warehouse early Saturday sending flames and smoke towering into the sky.

Oakland Fire Battalion Chief James Bowron said crews responded to calls reporting the fire in a commercial building at East 12th St and 45th Ave. late Friday night.

READ MORE: UPDATE: Many in East Bay Still Without Power

“Upon arrival, the two engine companies on the scene found a warehouse fully involved,” Bowron said. “A second alarm was called. We went to defensive tactic.”

Firefighters battled the blaze from ladder trucks and hoses on the ground, attempting to keep it from spreading to nearby buildings.

“There was high amounts of excessive radiant heat,” Bowron said. “We had other buildings across the street starting to catch on fire, but we had engines in the right place to insure we had no extension or fire leaving the building of origin.”

READ MORE: Menlo Park Man Stabbed at Party

The fire is under investigation, but Bowron said the area has a lot of homeless encampments.

“East 12th, there are a lot of encampments, a lot of people living along the street here, so there has been some talk possibly there was an encampment fire that extended into the main building,” he said.

PG&E said the fire knocked out power to more than 1,000 customers in the area.

MORE NEWS: One Dead, Three Wounded In Early Sunday Morning Shooting In Oakland's Uptown Neighborhood

“We had a lot of transformers popping off and a lot of downed power lines in the area,” Bowron said.