MILBRIDGE, Maine (AP) — Maine officials are investigating a group of positive coronavirus cases among blueberry workers.

Four employees of Wyman’s who were working at a location in Milbridge have tested positive. It was the third cluster of coronavirus cases at a blueberry processing facility or farm in the state, the Portland Press Herald reported.

Maine Center for Disease Control and Prevention Director Nirav Shah said the workers were tested before they began work. The cases have come at a time when the state is struggling to fill agricultural jobs.