Service has been restored as far as Wilmington on on SEPTA's Wilmington/Newark regional rail line, as of 5 p.m.
However, trains are still not traveling beyond that, SEPTA said.
Just before Wednesday's rush hour began, all service on the line -- which also serves Philadelphia suburbs including Darby and Chester -- had been suspended.
SEPTA said the disruption was due to Amtrak signal issues.
That same line suffered month-long schedule changes this year. On May 2 a freight train carrying crushed stone derailed on it, which required emergency repairs that lasted into June.
