( 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 . The four-car train was on a routine maintenance run with an experienced operator at the controls , but at the time of the incident , it was being run in automatic mode under computer control , BART said . The cars were being moved back to a train yard after having been cleaned of graffiti , Oversier said . There were a number of other personnel on the train at the time , but officials have not had an opportunity to speak with them , Oversier said . All train cabs are equipped with video cameras . Victims were experienced employees , BART says . The victims had extensive experience working around moving trains , the transit authority said . The procedures involved in track maintenance require one employee to inspect the track and the other employee to act as a lookout for any oncoming traffic , it said . They were supposed to stay clear of the track and be able to clear the operating area within 15 seconds of a train reaching them , Oversier said . BART 's union workers are currently on strike over a variety of issues , including wages . Oversier would not answer questions related to the strike , saying those issues were not at the forefront Saturday evening . He did say the BART employee who was killed was a member of American Federation of State , County and Municipal Employees , one of the striking unions , adding only that the man `` chose to come to work . '' Another of the striking unions , Amalgamated Transit Union Local 1555 , said it would not picket Sunday out of respect for the victims ' families . `` This is a tragedy of the greatest proportions for the BART family , '' Oversier said . Saturday was the second day of the strike that has paralyzed the San Francisco area . BART workers went on strike for four days in the summer over the same issues . The BART system normally serves 26 communities , including San Francisco and Oakland . It has chartered buses during the strike , but those help only a fraction of the roughly 400,000 people who use the service each day .
NEW : Train was returning to yard after being cleaned of graffiti , BART official says . NEW : The workers were supposed to stay clear of the track , official says . NEW : One of the victims was a union worker who `` chose to come to work , '' BART says . They were inspecting a possible slight dip in the rail .