LOS ANGELES (CNS) — A fire damaged a restaurant under renovation on the ground floor of a high-rise building in downtown Los Angeles Monday, and a man working in the business suffered critical burns.

The fire was reported about 8:30 a.m. at 255 S. Grand Ave., and firefighters quickly extinguished the flames, said Margaret Stewart of the Los Angeles Fire Department. The cause of the fire was under investigation.

"Per protocol for an incident of this nature, the LAFD Arson and Counter-Terrorism Section responded and it is an open, active investigation," Stewart said in a statement.

More than 120 firefighters were assigned to the firefighting effort, Stewart said.

"Upon arrival, firefighters saw heavy, white pressurized smoke billowing out from the ground floor restaurant ...," Stewart said. "Due to the size of the structure and high potential for life hazard, an additional five task forces were requested to include the airborne firefighting companies."

Firefighters set up a command post and checked the status of the elevators and fire alarms.

Crews were able to contain the fire in the restaurant, preventing it from spreading to any of the 20-plus floors above, Stewart said.

"Firefighter/paramedics located one adult male outside the building with significant, critical burn injuries," Stewart said. "The patient had been working within the restaurant under renovation."

Paramedics took the man to a burn treatment hospital, Stewart said.

"Once firefighters confirmed there was no remaining fire, the incident shifted to the search and evacuation phase because smoke was infiltrating the building and visible exiting the top at the roof line," Stewart said.

The building, constructed in 1988, has several ground-level restaurants with three floors of business and the remaining 23 floors are residential, Stewart said.

The residential floors include nearly 400 units with more than 700 residents, Stewart said.

"There were numerous reports of people needing assistance both in their units and stuck elevators," Stewart said. "All elevators were successfully recalled and a handful of people safely exited, none required any medical aid."

Firefighters checked to determine if anyone else in the building needed help, and a woman was taken to a hospital as a precaution for "smoke exposure," Stewart said.

"Individuals who evacuated up to the roof top were escorted back down through the stairwell and out of the building," Stewart said.

"Ultimately, approximately 60 people were evacuated from the structure and remained out until the building was safely cleared of all smoke and deemed safe to occupy by the Los Angeles Department of Building and Safety," Stewart said.