LAS VEGAS >> A two-alarm fire that caused minor damage but forced the evacuation of guests from upper floors of the downtown Golden Nugget Hotel and Casino was intentionally set, a hotel official said Thursday.

A hotel guest hospitalized in critical condition after he was found unconscious in a 22nd floor room where the fire began should not have been in that part of the hotel because it was being renovated, Golden Nugget spokeswoman Tiffany Hauck said.

“It was intentional,” Hauck said, but added that fire investigators had not told hotel officials how the fire started.

The man’s name wasn’t immediately made public. He was taken to University Medical Center in Las Vegas for treatment of smoke inhalation after fire sprinklers quelled the fire about 8:30 a.m., Las Vegas fire spokesman Tim Szymanski said.

Auto rental company worker Rudy Boteo was in a parking structure between the casino’s four towers when the first fire engines arrived. Minutes later, paramedics wheeled a gurney with the injured man from the 25-story Rush Tower to an ambulance.

“I looked up and saw smoke coming out,” said Boteo, who photographed the scene on his cellphone. “Then I looked down and saw them bring this guy out.”

Arson investigators didn’t immediately report how the fire started. Hauck said damage was estimated at less than $1,000.

About 60 people evacuated the 21st floor, and nine more left suites on the top floor of the newest tower in the hotel, Golden Nugget spokeswoman Amy Chasey said. The 22nd, 23rd and 24th floors were being renovated.

Ground-floor casino play was not interrupted.

Houston residents Brian and Julie Fenske and their two teenagers descended 24 flights of stairs after security told them to leave their 25th floor suite. They took the evacuation in stride.

“It would have been worse going up,” Julie Fenske said outside the hotel.

But the Fenskes reported about 15 minutes of confusion during which alarms gave conflicting instructions to remain in their room and then to evacuate before officials arrived at their door.

Hauck said an all-clear was given after hotel officials were initially unable to find a fire, and the evacuation order was given after fire was found.

The alarm brought dozens of firefighters from Las Vegas, North Las Vegas and surrounding Clark County to the 2,345-room casino in the center of the downtown Fremont Street casino district.

It was the second fire in seven weeks at the Golden Nugget.

Automatic sprinklers quelled a Jan. 27 fire in a dishwashing unit in a fifth-floor banquet area of the hotel. Officials said at the time that smoke from that fire prompted the evacuation of hundreds of people for about 30 minutes, but little damage was reported. The fire was ruled accidental.

Hotels in Las Vegas and Clark County are required to install fire sprinklers by tough fire codes instituted following two deadly high-rise hotel fires on the Las Vegas Strip more than 30 years ago.

The MGM Grand hotel blaze in November 1980 killed 87 people and was the nation’s second-deadliest fire at the time. An arson fire at the Las Vegas Hilton nearly three months later killed eight people.

A spectacular fire in January 2008 burned the outside fagade of the Monte Carlo resort on the Las Vegas Strip. Some 6,000 guests and employees were evacuated, and officials reported 17 people were treated for minor injuries and smoke inhalation. The fire was blamed on a welding accident.