The worst high-rise fire in Los Angeles history raced through five floors of the city's tallest building early Thursday, killing one person, injuring at least 40 and forcing others to flee to the roof where they were rescued by helicopter.

Firefighters found a body in an elevator on the 12th floor more than an hour after the inferno at the 62-story First Interstate office building was brought under control, City Fire Department spokesman Jim Wells said.A witness said she heard the victim, who was not immediately identified, screaming for help.

Zora Imamovic, 38, of Glendale, a foreman for a janitorial service, told reporters she was on the 58th floor when building security notified her on her walkie-talkie about the fire.

"We started going down the stairs, and smoke started going up. So we turned and went up," she said.

Imamovic said while she was headed for the roof she heard a building engineer talking over the walkie-talkie say he was also going to the roof. Then, she said, she heard him screaming, "Help, help, (elevator) car 33 is in flames."

The blaze started at 10:30 p.m. Wednesday and was extinguished four hours later. One-third of the city's firefighting force was involved in battling the blaze.

At least 40 people suffered smoke inhalation, including 17 who were hospitalized. One of the injured, a 49-year-old man, was in critical condition. The rest were listed from fair to serious, hospital officials said.

Three of the injured were firefighters, one who suffered heat exhaustion.

The blaze sent black smoke billowing hundreds of feet into the night sky, blew out plate-glass windows and hurled burning debris and glowing glass to the streets below.

The fire started on the 12th floor. At its height, flames were shooting from the windows of the 12th through the 16th floors of the downtown building on Wilshire Boulevard, drawing hundreds of curious spectators despite the late hour.

One man was trapped inside when smoke prevented him from getting past the 50th floor. He was rescue after the blaze was extinguished by firefighters who made their way to him from the inside and walked him to the roof where a chopper flew him to a nearby hospital. He was in stable condition, Wells said.

Most of the 40 people in the building made their way to safety by taking elevators to the street level, while eight fled to the roof where they were rescued by helicopters shortly after the blaze began.

The cause of the fire was under investigation, and officials said the 5,500 people who work in the building were asked not to come to work Thursday. The bank said damage would run into the millions of dollars, and its public relations and advertising departments were destroyed.

Fire Department spokesman Ed Reed said the furious flames created their own wind - a fire storm - and sent temperatures in the area of the fire soaring to 2,000 degrees.

The fire was declared out about 2:30 a.m. PDT.