BERKELEY -- Crews are working to determine what caused an explosion and massive fire in about 100 recycling bins Wednesday afternoon under the University Avenue freeway overpass, snarling traffic along Interstate 80 for hours.

Berkeley Fire Chief Gil Dong said one homeless person had undisclosed injuries but was not transported to a hospital. No fire crew members were injured, he added.

The blaze, which began at 2:41 p.m., was controlled by 2:59 p.m., Dong said. Smoke could be seen for miles, and several streets around the fire, at Second Street and Hearst Avenue, were closed while fire crews and police worked the scene.

Investigators were still working to determine the cause of the fire. Dong said early reports that the fire was caused by an explosion at a drug lab were false.

Police said firefighters rescued two homeless men who were camping near the bins, which are in a locked storage space, surrounded by chain-link fence and owned by the city of Berkeley. Those men, who have not been identified, were questioned by police but were not arrested.

Dong said Caltrans would be checking on the condition of the overpass, which may have been damaged by fire or smoke in the blaze. There was no damage estimate available late Wednesday.

Berkeley police said that they had no reason to believe Wednesday's fire was connected to an April 12 fire on Second Street. That five-alarm fire caused roughly $9 million in damage to several businesses in the area.

Staff writer Doug Oakley contributed to this report.