Delorier said the cause of the fire is still under investigation by the fire marshal's office. It has been deemed "suspicious" until proven otherwise, she said.
A driver going by the site Friday night noticed smoke and the Ayer, Shirley and Harvard fire departments responded to a call around 10:30 p.m. Firefighters were at the scene until almost 4:30 a.m., Delorier said, so they could verify there was no gas main in the building.
"There were no injuries, thank god," she said.
Mass Development owns the building on Perimeter Road, which is one of many structures slated for demolition and redevelopment, Delorier said.
She said the building has not been occupied, to her knowledge, since the 1980s, when it was used as a child care center.
