Downed wires meant major headaches for commuters on SEPTA's Regional Rail lines Thursday morning.

The issue, which occurred between 30th Street and Suburban Stations, caused service suspensions and lengthy delays starting around 9 a.m., SEPTA spokesman John Golden said.

Service on lines that had been suspended was resuming by about 11 a.m., but delays of up to two hours were expected along the Airport, Chestnut Hill East, Chestnut Hill West, Fox Chase, Lansdale/Doylestown, Media/Elwyn, Manayunk/Norristown, Paoli/Thorndale, Trenton, Warminster, Wilmington/Newark and West Trenton Lines, according to SEPTA.

It was not immediately clear what caused the downed wires or how long it would take to repair them.

While awaiting updates, passengers quickly took to social media to voice their frustrations.

This story is developing. Check back for details.