A 36-year-old electrical mechanical helper for Metro suffered an injury to his right arm Thursday morning after he was shocked while working on a rail car at the Alexandria yard, according to the transit agency.

The worker is expected to be held overnight at Washington Hospital Center for observation but is doing okay, Metro spokesman Dan Stessel said. Metro did not release his name. The worker was reported to be “conscious and alert the whole time,” Stessel said.

The cause of the incident is under investigation, he said.

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