A lack of sprinklers on eight consecutive floors allowed a small fire to grow into a high-rise inferno that killed three firefighters, the city's fire commissioner said.

The fire that broke out Saturday night in One Meridian Plaza burned for more than 18 hours, gutting nine floors of the building located across the street from City Hall. Sixteen firefighters were injured.Investigators went into the still-smoldering building Monday , accompanied by structural engineers who will try to determine how sturdy the building is.

Final extinguishing of hot spots and cleanup will not begin until the engineers are finished, said fire Commissioner Roger M. Ulshafer.

"We're concerned that the cold water on the hot steel up there will cause further contraction and expansion and then give us a collapse," he said. "We're going to let the building cool down normally and probably go up there for final extinguishment sometime (Monday)."