Updated at 2 p.m. ET
A fire at an oil refinery in South Philadelphia caused a series of explosions before dawn on Friday, unleashing a giant ball of flames and plumes of smoke into the air. The incident prompted a shelter-in-place order for a nearby neighborhood and sent more than 100 firefighters to the scene.
Several people were treated on the scene for minor injuries, WHYY's Tom MacDonald reported.
The fire is "confined and being addressed, but it is not under control," Philadelphia Deputy Fire Commissioner Craig Murphy said at a morning media briefing. He said Murphy said the shelter-in-place order was lifted after test samples of the air revealed no danger to the public.
Fire Commissioner Adam Thiel noted that it "is standard practice when fighting a fire of this type to let the flammable gases burn away in a controlled fashion."
Dramatic video posted on Twitter shows the sheer size of the fireball:
It wasn't immediately clear what started the fire.
Murphy said city firefighters responded just after 4 a.m. Friday and found a vat burning at the Philadelphia Energy Solutions facility. Firefighters working for the energy company were already on the scene.
Murphy said the vat contained butane; a company official later told The Associated Press that they thought it was primarily propane.
"They were doing some kind of work," Murphy said, "somewhere in the vicinity of that [vat] but not close enough for there to be bodily injury from the explosion."
The AP, citing company spokesperson Cherice Corley, reported that "three explosions, felt for miles away, went off as the fire worked its way through the tangle of pipes carrying fuel across the complex." Philadelphia Energy Solutions did not immediately respond to NPR's request for comment.
The company says its oil refining complex, which processes about 335,000 barrels of crude oil daily, is the largest on the U.S. East Coast.
This is the second fire reported at the refinery this month. A blaze on June 10 appeared to be smaller, and the company said at the time that it was "quickly contained and safely extinguished," as WHYY reported, and neighbors reported seeing smoke rising from the facility.