A stubborn fire raged for 5 and falf hours on the 29th floor of a historic downtown skyscraper in Chicago, shooting flames from windows and sending at least 37 people to hospitals, most of them firefighters who suffered smoke inhalation. Some injuries were serious, but city officials confirmed Tuesday that there were no deaths.

Streets around the Art Deco-style building, the corporate headquarters of LaSalle Bank in the city's downtown Loop business district, were closed to pedestrians and traffic as officials investigated the cause and tried to determine if the building was structurally sound.

More than 300 firefighters battled the blaze Monday night, shooting water into the windows and sometimes standing on the building's wedding cake-like tiers to gain better access. Office workers who escaped the blaze in the 43-story building said firefighters escorted them through blinding smoke to safety.

Of the 37 people injured, 22 were firefighters in moderate to serious condition, said fire commissioner Cortez Trotter. Most were being treated for smoke inhalation or minor injuries, officials said.

Investigators sealed off the 29th floor to preserve evidence and allow engineers to ensure it is structurally sound, Chicago Fire Department spokesman Larry Langford said.

Fire and police officials going above the first floor had to be decontaminated so they didn't track anything into the scene -- a problem identified after a fatal Chicago high-rise fire 14 months ago that killed six people.

The fire at 135 S. LaSalle Street was reported about 6:30 p.m. and extinguished about midnight. Thick black smoke poured out of windows, and metal window frames were twisted by the heat of the blaze on the 29th and 30th floors.

More than one-third of the city's fire equipment was at the scene, and suburban fire departments sent crews into the city to act as backup.

About 3,000 people work in the building, but only 400 to 500 were in the building at the time of the fire, he said.

Lasalle Bank is one of the largest banks in the Midwest. Its building was originally named the Field Building, after Chicago retailer Marshall Field, whose estate developed the skyscraper in the early 1930s. It was designated a Chicago landmark in 1994.

Source: Agencies