Overhead power line problems disrupted service on some SEPTA Regional Rail lines Thursday morning.
Service was suspended for a time on the Manayunk/Norristown Line and remained suspended on the Chestnut Hill East Line as of 10 a.m. due the problems, triggering delays of up to 40 minutes on other lines.
Overhead power problems are often related to subfreezing temperatures, but SEPTA said that while the weather appeared to be a factor Thursday, rail officials were still reviewing the situation to determine the causes.
In extremely cold weather, overheard power lines can contract and even snap, experts say. Rails also can contract in a deep freeze, requiring trains to operate at slower speeds.