Amtrak has launched an investigation to find out how a New York-bound train took a wrong turn onto mass transit lines and wound up in the suburbs of Philadelphia.

Keystone train 664, carrying 130 passengers, left Philadelphia's 30th Street Station around 11:45 a.m. last Thursday and somehow navigated off of Amtrak-operated rails, Amtrak officials confirmed. The train operators apparently missed a signal.

The train traveled about four miles west along tracks used by the Southeastern Pennsylvania Transportation Authority (SEPTA) for its regional rail system.

The lost train eventually followed tracks for SEPTA's Cynwyd line and stopped at the authority's station in Bala Cynwyd, Montgomery County, Pa., officials said.

SEPTA and Amtrak both responded to the scene and the passengers were taken off of the wayward train.

"They took us the wrong way out of Philly now we are stuck with no power and no way to get back to Philly," Bridget Cook tweeted to the Amtrak Twitter account. She then posted the photo above.

SEPTA staff guided the train back to Philadelphia, where passengers were offered a ride on another train to New York.

"Everyone was very fortunate that at that time of the day there were no SEPTA trains on that track," said SEPTA spokeswoman Jerri Williams. "At no time were any of our riders in danger."

The Cynwyd line is a single 6.1 mile track that runs from SEPTA's Suburban Station in Center City Philadelphia to Bala Cynwyd, where it ends. It has the lowest ridership among the transit authorities 13 regional rail lines -- with a daily average ridership of 622 people.

Williams says the next train heading towards Bala Cynwyd was set to depart Center City at 12:19 p.m. that day.

"An investigation was launched and the crew has been held out of work until they can be fully debriefed and additional training can be conducted," said Amtrak spokesman Craig Schultz.

When the Amtrak train switched onto SEPTA's line, Williams says the authority's control center was alerted.

The train's operators would have also been told that the track was clear through an automatic signaling system. SEPTA did not authorize the train to come onto their tracks, Williams says.

Dr. Allan Zarembrski, Professor and Director of Railroad Engineering and Safety Program at the University of Delaware, called the incident "unusual."

He says, while only limited information has been released about the mishap, it could have been the Amtrak dispatchers that led the train astray.

“It may have been the case where a dispatcher may have switched the train onto the wrong track," he said.

He says based on the limited information about the mishap, he hasn't seen anything to suggest safety was compromised -- adding that SEPTA's signal system appears to have done its job.

"That’s what the signal system is designed for, that if a train is occupying the track, it notifies the dispatcher and other train not to proceed," he said.

The National Transportation Safety Board says they are not looking into the incident because they only investigate accidents.

NBC10 has also reached out for comment from the Federal Railroad Administration.

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