LEWISTON – Mold has been found growing in the walls of a hospital office building, but it’s unrelated to air problems that made employees sick last spring.

St. Mary’s Hospital evacuated and shut down a medical building on Campus Avenue, where more than 80 people work, on May 31. Some workers complained of headaches, coughing and congestion.

Most symptoms experienced by employees disappeared after the building was emptied, but one man was hospitalized due to respiratory problems.

Health inspectors ruled out chemotherapy chemicals in the building as a cause of workers’ illnesses. They took apart the ventilation system and even opened up and vacuumed the building’s computers looking for the cause of workers’ illnesses.

“We consulted everybody under the sun on this,” said Sean Findlen, a spokesman for St. Mary’s. But during the investigation, the hospital did find mold between the building’s outer brick facade and inner wall.

Findlen said driving rains brought water into the layers of the wall and caused widespread mold. While the mold was unrelated to the employees’ illnesses, it could still hurt air quality, officials said.

The inside of the building has been pressurized and sealed off from the outer walls so that air flows only from the inside out, preventing mold from circulating in the area, officials said.

The air is to be tested in coming days and weeks, and when the hospital is satisfied that the air is clear, the 80 to 100 workers who were evacuated will be allowed to return to the building.

“But we won’t reoccupy the building until the air levels are what we want them to be,” Findlen said.