A train derailment left a tanker car and boxcar leaning off a Philadelphia bridge early Monday morning.

Police and firefighters responded to the train derailment near the Schuylkill Expressway (I-76), between South and 34th Streets, around 12:30 a.m.

According to CSX spokesman Gary Sease, the 101-car freight train was headed from Chicago to Philadelphia when seven cars derailed on the Schuylkill Arsenal Railroad Bridge where it crosses over the Schuylkill Expressway and River from University City to Grays Ferry -- just south of the South Street Bridge. It is not yet known what caused the derailment.

Six cars carried crude oil, but no leaking was reported. Another car contained sand, according to CSX. A sand car and an oil tanker remained tipped over on the span of the bridge nearly 12 hours later.

No injuries were reported.

The U.S. Coast Guard brought in a 25-foot response boat from its Philadelphia station to enforce a safety zone in the river just south of the bridge and another team that monitors for pollution also responded to the scene. Local police firefighters and emergency personnel also responded to the scene as part of the city's emergency plan.

"CSX would like to thank Philadelphia emergency first responders who arrived at the scene quickly and took prompt precautionary action," said a statement from CSX.

Both directions of the Schuylkill Expressway were closed shortly after the derailment as crews worked to stabilize the cars. By 2:30 a.m. traffic began to move eastbound -- it would take another hour for the westbound lanes to reopen. There were intermittent lane closures during the day as well.

As SkyForce10 hovered overhead it appeared that some of the rails below the teetering train cars had broken. The cars that stayed on the track were removed as the leaning cars remained for hours.

In the aftermath of the derailment, city councilman Kenyatta Johnson is demanding answers regarding what caused the accident.

"This is unacceptable," he said. "Very unacceptable."

Johnson says he's received numerous complaints regarding the aging bridge where the derailment occurred. The bridge was built around the turn of the 20th Century and has since carried rail traffic for more than a century.

"They sent out a representative to one of our meetings and they acted like they were open to addressing some of the issues," Johnson said. "But to date they haven't come back to us to address any of those issues."

CSX officials say they are investigating the condition of the tracks, condition of the cars and how the train was operated. A spokesman also says any concerns from the public or a councilman receive high priority and that the company is more than willing to have a local rep meet with them. Johnson says he wants answers from CSX in order to protect Philadelphia residents.

"We're going to be calling for hearings in the city of Philadelphia asking specifically for CSX to tell the city of Philadelphia how they are maintaining their bridges, and how they are maintaining their railways," Johnson said. "They should assure the city of Philadelphia that their infrastructure is safe."

Another CSX spokesperson says the removal of all the cars could take up to two days.

"The safe removal of six of the cars will involved the careful and environmentally responsible transfer of oil to other tank cars or tanker trucks," the spokesperson wrote. "It also will require the removal of sand carried in one of the cars. These operations should begin this evening and continue until complete in the next 24-48 hours. These plans have been shared with public agencies, including the U.S. Coast Guard and Philadelphia Fire Department."