PHILADELPHIA — Hundreds of commuters were stranded at a regional rail station Thursday after service was suspended when a worker was struck and killed on the tracks, creating further havoc on the system already crippled by a transit strike.

The train was inbound from the city's northern suburbs when it struck the worker shortly after 9:30 a.m., Southeastern Pennsylvania Transportation Authority officials said. More than 625 people on the train were stranded at the Melrose Park station as three of 13 regional lines have had to be shut down, SEPTA spokeswoman Jerri Williams said.

Normally, when regional rail lines are shut down due to an accident, SEPTA buses arrive to take passengers to their destinations, Williams said. But that's not possible because the more than 5,000 bus, subway and trolley drivers are in the third day of a strike. Regional rail operators are members of a different union and are not on strike.

The shutdown of three regional rail lines cuts off much of the service to the northern suburbs, Williams said. The problem will likely worsen as more trains arrive, Williams said.

"We're talking about hundred and hundreds of people affected," she said, adding that the agency is trying to find ways to get the people to their destinations.

The accident is the second in two days on regional rail, which has seen a surge in ridership due to the strike.

On Wednesday, a regional rail car caught fire as it headed downtown around 7 a.m., causing delays and confusion. There were no serious injuries; SEPTA said neither accident was believed to be strike related.