Explosion rocks South Philadelphia oil refinery

An explosion struck a South Philadelphia oil refinery early Friday morning.

According to Fox29, the Philadelphia Energy Solutions oil refinery, near one of the city's sports complexes, experienced a massive explosion. The news station reports this is the second fire this month.

A public information officer for PES told firefighters a vent containing butane was the source of the explosion. It's unclear how many people were at the facility when the explosion occurred; at least one employee compained of chest pains, but didn't need to be transported to the hospital for further care.

Residents were told to shelter in place through the 7 a.m. hour.

A private fire company contracted by the refinery responded to the emergency.

The complex is one of the largest of its kind operating in the U.S. Eastern Seaboard, according to PES.

Photos and videos published on social media show the facility engulfed by a massive fireball - reported as a 3-alarm fire by local reports.

The refinery, established in the post-Civil War era, was once Philadelphia's biggest employer, according to reporter Steve Keely.

In 1975, eight Philadelphia Firemen died in an 11-alarm fire at the same location.

There were no immediate reports on possible fatalities or injuries.

This is a developing story. Check back for updates.