Fire leads to massive explosion at Philadelphia oil refinery

A massive explosion at an oil refinery in Philadelphia Friday morning could be felt from miles away. According to CNBC, four minor injuries had been reported.

What happened?

Around 4 a.m. ET, a vat of butane ignited at Philadelphia Energy Solutions, the outlet reported. It's not clear what caused the vat to catch fire. From there, the fire reportedly spread through the refinery's system of pipes. Smaller explosions occurred as the fire branched out. A spokeswoman for the refinery told WCAU-TV that the fire had mostly been burning propane.

After more than five hours, the fire was contained but still burning. People who lived near the refinery were initially warned to take shelter due to concerns about dangerous chemicals that might be present in the smoke from the inferno. Philadelphia Air Management Services later tested the air and determined that it was safe to breathe.

The force of the explosion could be felt across the Delaware River in New Jersey, according to WCAU, debris fell several blocks away.

The fire caused part of Interstate 76 and the city's Platt Bridge to temporarily be shut down. Around 120 firefighters responded to this incident.

Philadelphia Energy Solutions claims to produce roughly 335,000 barrels of crude oil every day. It also says that it's the largest refiner on the U.S. eastern seaboard, and the 10th largest in the country. The company filed Chapter 11 bankruptcy in early 2018. The company currently runs the refinery in partnership with Sunoco.

This same refinery caught fire on June 10. Nobody was injured in that early explosion, but it led to environmental activists protesting the refinery's safety standards.