A Metro train derailed at an Alexandria railyard Monday afternoon, apparently after a worker failed to remove a safety block from underneath one of the wheels designed to prevent it from accidentally rolling.

No one was injured in the incident, the agency said.

“Preliminarily, it appears that personnel neglected to remove one of the chocks that was under the wheel,” Metro spokesman Dan Stessel said.

The derailment occurred when a 3000-series railcar was being moved out of a workshop building at a slow speed, Stessel said. One set of wheels went over a wheel chock — a safety device intended to immobilize the wheels — and came off the rails, causing minor damage to the car and tracks but resulting in no injuries or effects on train service. Stessel called the incident “really minor.”

The employee responsible for removing the wheel chock has been removed from service while Metro safety officials investigate the incident.

“Any discipline would be determined only after the investigation is concluded,” Stessel said.

Safety chocks have been an area of focus for Metro staff in recent months, after a Federal Transit Administration report issued in August criticized the agency for failing to consistently use wheel chocks and hand brakes while storing trains.

In that report, the FTA urged Metro supervisors to enforce the widespread use of wheel chocks at railyards — in part to prevent derailments or safety mishaps that could endanger workers.

“Preventing unintended movement of rail vehicles is fundamental to safety and [the Washington Metropolitan Area Transit Authority] needs to do more to eliminate these types of incidents from happening,” then-U.S. Transportation Secretary Anthony Foxx said in a statement at the time. “Verifying that a train has been properly secured is a common sense solution to prevent accidents.”