A billowing fire and series of explosions at a South Philadelphia oil-refining complex, the largest on the Eastern Seaboard, shook homes as far away as southern New Jersey on Friday morning.

The blaze started in a vat, which exploded and prompted other explosions as the flames engulfed fuel pipes at Philadelphia Energy Solutions (PES) refinery, officials said.

One person was treated by emergency responders at the scene, and four people were treated by on-site company medical personnel, officials said. No one was seriously injured.

The fire was reported at 4:05 a.m., and by about 9 a.m. had been contained but was not yet under control, according to a statement from the company. City and company crews were also working to cool surrounding tanks to keep the fire from spreading.

"PES is following protocol to protect the environment, its employees, and the surrounding community to bring the incident to a safe conclusion, and minimize any impacts from the event," which included three explosions, the statement said.

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The cause of the fire was under investigation, but officials believe mostly propane was burning.

Residents east of the refinery complex were asked to shelter in place for about three hours, and roadways in the area remained closed as the morning rush hour began so that crews could respond.

The Philadelphia Department of Health said preliminary air samples came back with no signs of ambient carbon monoxide, hydrocarbons or hydrogen sulfides, and that further tests would be done to assure the air was safe.

Some South Philadelphia residents said art came flying off their walls from the explosions, according to NBC Philadelphia.

People could see the blaze from miles away , and those close to it said debris clouded the early morning sky.

The complex is made up of two refineries, Girard Point and Point Breeze, and processes 14 million gallons of crude oil a day. The fire started at Girard Point.

On June 10, a small fire was ignited at the complex, but no one was injured, according to NBC Philadelphia. The complex also had a fire in 2015.

Protests followed the fire earlier this month, as environmentalists and area residents raised concerns about the facility's safety.

Philadelphia Mayor Jim Kenney said the company and fire department officials told him that Friday's fire and the June 10 fire were "unrelated in their nature and cause."

But one community organization called the effect of the fires and explosions "unacceptable."

"It is unacceptable that Philadelphia residents had to wake up in the middle of the night fearing for their lives from the explosion at PES," said a statement from Philly Thrive, an organization of residents who live near the plant and has been protesting against it since 2015.

"Do you know how scared I was this morning to be shaken out of my sleep by the explosion?" Sonya Sanders, a member of the organization, said in the statement. "I do everything I can to close my windows and keep this pollution out of my house. But when these fires happen it shows there really is nothing we can do to protect ourselves."

"We have the right to breathe clean air and we need to hold the refinery accountable for what they're putting out into the community," said another organization member, Sylvia Bennett.

Mayor Kenney said, "I believe that there is room for improvement," and added that he was working to set up a meeting with PES leadership to address concerns, especially surrounding air quality.

“Those who live and work in close proximity to the refinery and all Philadelphians have our word — we are firmly committed to ensuring the safe operation of the refinery, and the safety of those in its vicinity," Kenney said.

The refinery was operating at a reduced rate Friday, according to PES.