PHILADELPHIA — Streets are closed in Philadelphia's Old City neighborhood after residents reported hearing two explosions that blew manhole covers out of the ground.

A spokeswoman for the electric utility company said utility crews are on the scene trying to determine what happened. She says smoke and heat damaged four manhole covers early this morning but the electricity provider hasn't determined if there was a fire or explosion. No injuries were reported.

Witnesses said they heard two loud explosions and saw thick smoke billowing from the damaged manholes. A three-block stretch of Market Street and one block of Second Street remained closed as of 6 a.m. Streets were expected to be closed for several more hours while crews investigate the explosions.