The ceiling at the Longhorn Steakhouse near the Maine mall collapsed on Friday during the dinner service.
Members of the South Portland Police and Fire Department arrived at 6:40 p.m., the departments said in a joint release.
Employees at the restaurant noticed the ceiling tiles starting to fall and moved patrons out of the way before the ceiling came down.
The Portland Press Herald reports that fire chief Phil Selberg estimated that 150 people were in the restaurant when the ceiling collapsed.
The building is currently being evaluated by the inspectors with the South Portland Code Enforcement Office, the departments said.
