U.S. investigators examining the fatal collision in Virginia between a truck and an Amtrak train carrying Republican lawmakers are looking at possible problems with the equipment that warns motorists not to cross when a train is coming.

National Transportation Safety Board officials in a briefing on Thursday said that they’re taking electronics from the grade crossing to the agency’s Washington laboratory and hoping to talk to more witnesses in an attempt to determine if a malfunctioning warning system could have played a role in Wednesday’s violent crash.

The safety arms that prevent vehicles from entering the rail crossing were malfunctioning a day earlier, several residents near the Crozet, Virginia, crash site told the Associated Press.

When asked if NTSB’s investigators had heard the reports, chief investigator Pete Kotowski said: “Yes, from our witness reports, we have obtained some information about some issues that occurred at that grade crossing.”

One occupant of the truck was killed by the impact near Charlottesville and multiple people were injured, according to the NTSB and local authorities.

The Amtrak train was carrying GOP members of Congress to a retreat at a resort in West Virginia. It was traveling at 61 miles (98 kilometers) per hour, which is 1 mile per hour above the speed limit on that section of track, according to preliminary data from a recorder on the train.

The NTSB is still waiting to interview the train’s engineer and others. Investigators didn’t say how a grade-crossing malfunction might have led to the accident, and it can take a year or longer for the safety board to complete an investigation.