WASHINGTON (AP) – Soon after a commuter train fatally struck two track maintenance workers in Woburn, Mass., the train dispatcher told her supervisor, “It was my fault,” according to federal investigative documents released Monday.

The dispatcher’s comments are among voluminous interview transcripts, factual reports and other evidence about the Jan. 9 crash released by the National Transportation Safety Board.

Officials are probing why the train was on the track where the crew was working, when earlier trains had been switched to parallel tracks.

The dispatcher used a commuter program as part of the system to block sections of track undergoing maintenance.

The train’s engineer called the dispatcher immediately after the crash to report his train had struck track equipment.

“The train dispatcher turned to her supervisor and said, ‘We hit some track equipment, and it was my fault. He hit track equipment, and it was my fault … I pulled down the wrong freaking block and we hit something,”‘ the NTSB’s report said.

A commuter train on the wrong track slammed into track maintenance equipment at 60 mph, killing two maintenance crew workers and seriously injuring two other workers. Ten passengers on the Lowell-to-Boston Massachusetts Bay Transportation Authority train also were hurt in the crash near a Woburn station.

Officials are investigating whether the track maintenance crew failed to install a required safety shunt on the tracks that could have warned approaching trains that workers were in the area.

Workers told investigators they usually used shunting devices only for big jobs. The crew that was struck had been replacing crossties, which was not considered a big job, they said.

The NTSB won’t offer its conclusions, including a determination of probable cause in the crash, until the final report is completed. No timeline was given for the final report.