National Transportation Safety Board (NTSB) officials investigating a Metrolink commuter rail collision that killed 25 people in Chatsworth, Calif., on Sept. 12, say they want to review cell phone records to determine if the engineer blamed for running a stop signal before the crash may have been text messaging, according to an Associated Press report.

The NTSB, which confirmed two days later that the engineer killed in the crash had failed to stop at the final red signal, says it is planning to review cell phone records of two 14-year-old boys and the engineer after the teens told a local TV station that they received a text message from the engineer shortly before the crash. The boys were reportedly part of a group of youths who befriended the engineer and asked him questions about his work.

The NTSB did not find a cell phone belonging to the engineer in the wreckage, but will request his cell phone records, as well as those of the two boys, according to published reports.

The commuter train carrying 220 people rolled past stop signals Friday before crashing head-on into a Union Pacific train in Chatsworth. The accident, which is the deadliest rail disaster in 15 years in the U.S., left train cars so mangled that some bodies had to be removed in pieces. The crash injured 138 people.

Services resumed Monday for the daily commute with Metrolink officials planning on using buses to complete trips in areas that are still closed due to the NTSB’s ongoing investigation. Regular riders said the number of commuters Monday was far short of a normal day, according to the Los Angeles Times.