A Norfolk Southern Corp. conductor was killed Tuesday in a collision with a truck in Cleveland, prompting an investigation by the US National Transportation Safety Board. 

The accident is the third investigation opened involving the railroad since the Feb. 3 derailment in East Palestine, Ohio, that led to the release of toxic chemicals. 

The NTSB said in a tweet that it’s sending a team to the scene of the latest incident. The conductor was killed at the Cleveland-Cliffs Cleveland Works facility, which makes flat-rolled steel, after being struck by a dump truck while a train was moving through a crossing at the facility, Norfolk Southern said in a statement. 

The truck collided with the front-left side of the first car in the Norfolk Southern train after first stopping at a stop sign at the tracks, according to the Cleveland police. The train’s conductor was outside of the moving rail cars and was struck during the collision. The truck was carrying a full load of limestone, the police said in a statement.

The police identified TMS International as the owner of the dump truck involved in the crash. The company, which provides on-site services to steel mills, is investigating the incident and cooperating with authorities, a spokesman said. 

The US safety board is also investigating a March 4 Norfolk Southern derailment near Springfield, Ohio.