A train derailment this month in Calhoun County was caused by a lack of required equipment, the National Transportation Safety Board said Monday.

The incident was among a series of derailments involving Norfolk Southern trains in a matter of weeks.

NTSB investigators said the March 9 event occurred because two of the train’s locomotives didn’t have the required alignment control couplers. The lack of equipment was not identified by a company inspection, the agency said.

According to the NTSB report, the derailment involved 37 rail cars, in addition to the two locomotives. The board reported two of the train’s six locomotives were “waybill locomotives.” This means that the two locomotives were not being used for any tractive power.

The report also said the rail cars had no alignment control couplers, which are designed to “resist lateral coupler movement under compressive in-train forces.” Norfolk Southern forbids towing waybill locomotives without the couplers.

“We have taken immediate action to update our manuals with photos and details to implement training with our crews,” said Connor Spielmaker, a Norfolk Southern senior communications manager. “Safety is a priority at NS and we’ll continue working with the NTSB to identify the final cause of this derailment and implement any other necessary changes.”

There were no injuries reported in the Calhoun County derailment. Three derailed tank cars on the train did contain hazardous material residue but nothing leaked from the cars.

Austen Shipley is a staff writer for Yellowhammer News.