A Northeast Philadelphia man was the victim of an incident on the Broad Street Line on Monday night that killed one SEPTA worker and injured another.

Darren Monroe, 54, was killed when struck by a train about 5:45 p.m. Monday, Philadelphia police reported. He had worked for SEPTA for 17 years.

Monroe and the man who survived were conducting a track inspection and doing light maintenance, said James Southworth, who is leading the investigation for the National Transportation Safety Board (NTSB). The Broad Street Line has four tracks at the site of the accident and two additional loop tracks.

A northbound train hit Monroe, Southworth said. It was unclear if there were trains running on the track the men were working on, or if he was hit by a train on an adjacent track, the investigator said. The men were wearing reflective vests and hard hats.

An initial police report stated Monroe tripped and fell backward into the path of a train, but officials could not confirm that account Tuesday.

Investigators from the federal agency would determine what safety precautions were in place for the workers and whether there were other personnel on the tracks. The investigation would include a review of the front and rear cameras on the train, and a camera placed within the control cab to monitor the operator. NTSB personnel would also interview the man who survived the incident.

The extent of his injuries were not clear Tuesday, Southworth said.

Safety procedures for subway lines are established by the Federal Transit Administration, he said, but there are several ways to provide protection for workers on subway tracks.

In recent years, the NTSB has twice issued recommendations after deaths on subway tracks. Two New York City flagmen were killed by a subway train in November 2016 while they set up a light system to alert trains to the presence of a contractor. The federal agency recommended improved communication and slower speeds when there are flagmen on the tracks. In October 2013, two track workers were killed in Walnut Creek, Calif., by a train. In that incident, the NTSB immediately warned the Bay Area Rapid Transit system to install equipment to alert trains and dispatchers to the presence of workers on the tracks, and design a more comprehensive system of protection when workers are on the tracks.

The NTSB’s investigation into the death began Monday night, and investigators for the agency were in Philadelphia by 7:30 a.m. Tuesday. Their review will include looks at the equipment and vehicles in use, SEPTA’s rules, and worker protections, and the dispatch and train control operations at the time of the incident. Investigators are expected to visit the site of the impact Tuesday night, and Southworth said some service shutdowns may be necessary to accommodate the investigation.

“We like to get things done as quick as we can,” he said, “because there’s so much to do.”