Eric Jamison, Associated Press
Fire damage scars the facade of the Monte Carlo hotel and casino in Las Vegas. No cause has been found yet for the three-alarm fire that broke out Friday.

LAS VEGAS — The burned exterior facade along the roof of the Monte Carlo hotel-casino will have to be removed or secured before the Las Vegas Strip resort can reopen, the chief county building inspector said Saturday.

Ron Lynn, chief of the Clark County Building Department, said the 32-story building will remain closed until resort owner MGM Mirage Inc. completes work to the roof-line foam building material damaged in Friday's blaze.

A spokesman for the casino company said he could not immediately say how long that would take. "Now that the county inspectors have completed their work, we'll begin our assessment," MGM Mirage spokesman Gordon Absher said.

Lynn and an assistant Clark County fire chief, Sandra Baker, said most fire damage was to the exterior of the top five floors of the 3,213-room hotel. The roof was not damaged, they said, declining to estimate repair costs.

"The building is in a safe condition," Lynn said. "We feel it's habitable from the casino up through the 26th floor."

The cause of the three-alarm blaze remained under investigation, Baker said.

Officials said Friday that welders were on the roof, where Lynn said the hotel had a permit to install window washing gear. Baker said she did not know what role, if any, workers may have played in starting the blaze.

Seventeen people were taken to hospitals with what ambulance company officials described as minor injuries, mostly from inhaling smoke or fleeing the building. One remained hospitalized Saturday in fair condition, Clark County spokesman Dan Kulin said.

The 120 firefighters who fought the blaze were unhurt, despite having to break windows and lean outside to spray water on the fire.

Baker said a fire standpipe system delivered water to the top floors of the hotel — well above the 10 or more stories that fire department ladders could reach.

Helicopter water drops would have been impractical and imprecise in the urban area, she added.

Guests were allowed back into the hotel late Friday and Saturday with security escorts to retrieve items left when they fled, officials said. Absher said MGM Mirage found rooms for displaced guests at its other hotel-casinos.

Absher said about 2,800 employees work at the Monte Carlo, and almost 1,000 were in the building when fire broke out.

He estimated 5,000 guests were staying at the hotel, but said he did not know how many people were in the casino, restaurants or spa at the time.