(CNN) -- An out-of-service Bay Area Rapid Transit train struck and killed two workers on a section of track northeast of San Francisco on Saturday afternoon, the transit authority said. The employees were making track inspections near the Walnut Creek station, BART said in a statement. One was an employee and the other a contractor. Their names were not immediately released. "Our hearts and prayers go out to the families of the two workers who've just been killed on the BART tracks," BART General Manager Grace Crunican said. She said the accident is under investigation. Paul Oversier, BART's head of operations, told reporters that the two workers were looking into a possible slight dip in the rail when they were hit.
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NEW: Train was returning to yard after being cleaned of graffiti, BART official says
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NEW: The workers were supposed to stay clear of the track, official says
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NEW: One of the victims was a union worker who "chose to come to work," BART says
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They were inspecting a possible slight dip in the rail
Saturday was the second day of the strike that has paralyzed the @placeholder area.