A massive explosion rocked the Sunoco refinery in Claymont, Del. late last night, sending flames shooting into the sky and initially raising concerns about residents' safety in Pennsylvania, Delaware and South Jersey.

Shortly before midnight, a company official said Sunoco and local fire officials were fighting the blaze and that no injuries had been reported.

Although there had been early talk of possible evacuations, none took place because any possible harmful ingredient of the chemical that was released into the air - ethylene - burned off, said Cpl. Jeff Whitmarsh, a spokesman for Delaware State Police.

By 1:30 this morning, the fire was contained but still burning."

"We're very fortunate and grateful there were no injuries," said Thomas Golembeski, a spokesman for Sunoco, at what was a chaotic scene at the Claymont facility of Sunoco emergency response officials, local firefighters and harried residents.

Residents reported hearing one or two explosions that rattled car and house windows at about 10:15 p.m. Flames could be seen as far away as Philadelphia International Airport.

"All I know is that there are a million pipes down there and I did not want to wait for another explosion," said Debbie Collison, a resident of nearby Linwood who could see the flames from a window in her home. She fled that house in a car with her son, his girlfriend, a next-door neighbor, two cats and a dog. She described the explosion as a "ba-boom."

Collison and a union official said there had not been an explosion like this for a long time, perhaps decades, in the heavily industrialized area.

Police blocked off roads around the bi-state refinery, one of the largest in the Northeast in a heavily populated area just off I-95. It is major producer of gasoline and chemicals.

There was initial confusion about the origin of the explosion, but it appeared that it took place in a small part of the refinery in Claymont Del., just south of the main refinery in Marcus Hook, Delaware County. There were also mixed reports over what type of chemical was airborne.

TV initially reported the chemical in the explosion as ethylene oxide, a toxic material used in auto antifreeze. A Sunoco official later identified the chemical as ethylene, a byproduct of oil refining used to manufacture plastics.

Sunoco officials did not have an official cause of the fire.

The explosion came three days after Pennsylvania fined the Marcus Hook refinery $762,150 in civil penalties for air-quality permit violations.

"Sunoco emitted nearly twice the permitted limit of particulate matter and an average of four times the permitted level of ammonia from a unit at this facility for more than one year," Environmental Protection Southeast Regional Director Joseph A. Feola said in a statement. "We take these violations very seriously, and are working with Sunoco to correct the problems."

The problems were discovered in tests done by Sunoco in 2006.

Contact Bob Fernandez at 215-854-5897 or bob.fernandez@phillynews.com.

Inquirer Photographer David Swanson contributed to this report.