Amtrak service between Philadelphia and Washington was disrupted through the morning rush hour Wednesday after two CSX workers were fatally struck by a train in the nation's capital.

Service was suspended overnight and through the start of the morning rush period due to the investigation, with more delays lingering, Amtrak said.

Trains began resuming operations around 9 a.m. Wednesday, the rail agency said. Some trains were running at lower speeds.

The two workers were struck in the track area about 11:50 p.m. Tuesday on the 1200 block of New York Avenue Northeast and died at the scene, according to District of Columbia Fire and Emergency Services. A third railroad employee was being taken to a hospital for a checkup, fire officials said.

The two freight train conductors had gotten out of their train near Union Station to check out an alert about a problem with one or more of the wheels, National Transportation Safety Board member Earl Weener said at a Wednesday news conference

An investigation is ongoing and there are "few definitive facts at this early stage," Weener said.

The workers' names were not immediately released.

"Our thoughts are with the families and friends of our employees," CSX spokesman Rob Doolittle said in an email. "CSX management representatives responded to the scene to assist with the investigation of this tragic incident."

The CSX train that the employees got off of was coming from Baltimore and was the type that carries shipping containers, Weener said.

Amtrak Train 175 was carrying 121 passengers when the incident occurred, the Washington Post reported. There were no injuries to passengers or crew.

Riders may check the status of their trains on Amtrak's website or mobile app.

This article contains information from the Associated Press.