A MARTA contractor died after being struck by a train near Medical Center Station Sunday night.

Robert Smith of Griffin, 38, was working on a rail line when he was struck by a northbound train before 9 p.m., the agency reported. He was in his work vehicle at the time.

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The incident is impacting service at a Sandy Springs station.

It’s unclear what caused the accident or why Smith was on the tracks at the time. MARTA spokeswoman Stephany Fisher said the agency is investigating. No injuries to train passengers or operators were reported.

Fisher said the agency has safety protocols to protect people working near railroad tracks, but declined to elaborate.

“There needs to be an investigation so we can determine if the protocols were followed,” she said.

Smith’s employer, Cleveland Electric Company, released a statement Monday calling the incident “a tragic accident.”

“Electrician Rob Smith was a long-time employee with an exemplary record of service to our company and to our clients,” the company said.

“At the time of the accident he was performing normally scheduled work for MARTA,” the company said. “We are heartbroken by this accident and our focus at this time is with his wife, children and other immediate family members.”

The incident shut down portions of MARTA’s red and gold lines until just before 6 a.m. Monday. The agency used a bus bridge to transport passengers until the rail lines reopened.

It’s not the first time a MARTA train has struck and killed a worker. In 2000, three MARTA employees died in two separate incidents.

In the first, one worker was killed and another injured when they were struck as they inspected a section of track near Avondale Station.

A little over a month later, a father and son – both MARTA contractors – died after they were struck while repairing ceiling tiles at Lenox Station. MARTA later paid their family a $10.5 million settlement.