A fireball from a Sunoco oil refinery blast lit up the Sunday night sky along the Delaware River, but officials said there were no immediate reports of injuries and no evacuations.

Television helicopter footage from several stations showed fire trucks spraying down flames shooting high into the air at the complex straddling the Delaware/Pennsylvania border.

Fire and police agencies from both states responded.

Jeff Whitmarsh, a spokesman for Delaware State Police, said the explosion happened about 10:15 p.m. on the Delaware side of the border.

"Everyone on site has been accounted for, and no injuries in connection with this incident have been reported at this time," Sunoco Inc. spokesman Thomas Golembeski said.

Whitmarsh said shortly after midnight that the fire had been contained but was not out.

New Castle County, Del., county councilman John Cartier said he could see the flames from his home at least three miles from the refinery.

"It was almost like seismic," he told The (Wilmington) News Journal. "My house was rocked. It was a big large boom."

Authorities were still trying to determine what caused the explosion, which occurred at the refinery's ethylene complex. Ethylene is a feed stock used in the production of plastics. A Sunoco chemical plant adjacent to the refinery produces polypropylene.

Golembeski said the explosion and fire was contained to the ethylene unit inside the refinery and did not affect the chemical plant. He said he did not know if the explosion would affect production at the refinery or the chemical plant.

"It will be some time before we know the exact cause of what happened," said Golembeski, who could not say whether the explosion happened in a pipeline or a storage tank.

"Right now, we're working on putting the fire out," he said.

According to the company's Web site, Marcus Hook processes about 175,000 barrels of sweet crude oil per day into various petroleum products such as gasoline, jet fuel and home heating oil.

That's about 1 percent of the nation's 17.5 million barrels of daily production.

According to the most recent U.S. Department of Energy ranking of the nation's 150 operable refineries, Marcus Hook is ranked 39th for total production.

The refinery sits on a 781-acre site along an international seaport, and it operates around the clock seven days a week with about 700 employees. It refines oil primarily from fields in the North Sea and West Africa.