A massive fire ripped through a Pennsylvania oil refinery early Friday... triggering a huge explosion that local media said rocked homes several miles away.

This is the second fire this month -at the Philadelphia Energy Solutions refinery, which processes 335,000 barrels of crude oil every day.

The complex- one of largest and oldest on the east coast--employs around 1,000 people but there were no immediate reports of casualties.

While the blaze has been contained- the city's Fire Department is asking residents and businesses in south Philly to shelter in place until further notice.