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A fourth worker at Bath Iron Works has tested positive for COVID-19, the shipbuilding company said in a brief statement released on Thursday.

The person was last at work on June 18, and workers who came in close contact with them have been told of the case, according to the statement.

It was unclear whether the case was among the 53 cases announced by health officials on Thursday ― the most new cases reported since June 12. That brings the total number of cases detected in Maine since the outbreak began in March to 3,070 cases, according to the Maine Center for Disease Control and Prevention. That’s up from 3,017 on Wednesday.

BIW’s third case was a vendor who worked at the facility for several months who tested positive for the coronavirus on May 25, was placed in quarantine and received medical care. The first cases were announced on March 23 and on April 2. Both people returned to work, BIW said. The status of the third worker was not immediately available on Thursday.

The announcement comes with the largest union at BIW, the 4,600-member International Association of Machinists and Aerospace Workers Local S6, out on strike since Monday.