BRUNSWICK — The Bath Iron Works’ Cross Building off Bath Road was evacuated Thursday morning after a small propane leak in a heating unit was discovered.

Firefighters responded just after 8 a.m. and found no elevated levels of natural gas in the building, according to Brunswick Fire Lt. Steve Emmons.

Only 30 percent of the workforce in the building was present, Emmons said he was told.

Maine Natural Gas responded, and employees were able to return to the building in about two hours.

“We were able to contain the leak to the building, and they were able to be back online when we left,” Emmons said.