WEST READING, Pa. -- Firefighters battled a blaze in Pennsylvania Friday after an explosion at a chocolate factory injured at least six people and sent a plume of black smoke into the air above West Reading.

Berks County fire crews remained on the scene at the R.M. Palmer Co. plant Friday night about 60 mile (96 kilometers) northwest of Philadelphia, but few details had been released.

Six injured people were taken to Tower Hospital in West Reading, NBC10 in Philadelphia first reported.

Officials at Tower Hospital did not immediately respond to phone messages or emails from The Associated Press seeking comment.

The explosion occurred shortly before 5 p.m. in a building at the plant at Second Avenue and Cherry Street. Debris covered roads in the area, NBC10 reported.

West Reading police referred calls to the Berks County communications center. A Berks County emergency dispatcher told the AP Friday night that six people were injured but couldn't confirm they had been hospitalized and had no other information.