HOUSTON » Four firefighters searching for people they thought might be trapped in a blazing Houston motel and restaurant today were killed when the part of the structure collapsed and ensnared them, authorities said.

At least five other firefighters were hospitalized in the blaze that became the deadliest in the 118-year history of the Houston Fire Department.

Flames were shooting from the roof of the Southwest Inn, along one of Houston’s most heavily traveled freeways, U.S. Highway 59, and black smoke was blanketing the area as firefighters tried to extinguish the fire.

Three firefighters were killed at the scene, while the fourth died at a hospital, according to the mayor’s office and a medical examiner. Five other people were injured and were hospitalized for treatment of chest pains or leg injuries.

“We took the highest amount of risk possible because we thought we had civilians in the structure,” Fire Chief Terry Garrison said. “The structure collapsed and our members who were trying to save lives were lost.”

Garrison said everyone else has since been accounted for. A cause of the blaze hasn’t yet been determined.

The loss of life is the single worst in the history of the department, which had counted 64 firefighters lost since the city began paying firefighters in 1895. Twice previously, two firefighters were killed in a single fire, in 1953 and most recently in 2000. Three firefighters died in 1929 when a train slammed broadside into their engine.

“Unfortunately, the building had much more fire in it than we originally thought,” Garrison said. “We do know there was a collapse and it caused our firefighters to get trapped.”

When a flag-draped body was removed from the smoldering remains around 4 p.m., some four hours after the blaze broke out, firefighters — working in swirling winds, steamy humidity and temperatures exceeding 90 degrees — paused and saluted. A procession of ambulances, under police motorcycle escort, left the scene about 90 minutes later and made a ceremonial drive past the fallen firefighters’ station, by then draped in black.

“We will provide appropriate services to our fallen firefighters and full honors, but there is nothing we can do that will heal the hurt that we all feel today,” Mayor Annise Parker said. “I ask for every Houstonian to offer their prayers to the families of these fallen firefighters, and also to think about what the job of firefighter is and the dangers they face every day.”

The fire department identified the dead firefighters as Capt. Matthew Renaud, 35, an 11-year veteran of the department; Engineer Operator Robert Bebee, 41, who joined the department almost 12 years ago; Firefighter Robert Garner, 29, who joined the department 12½ years ago; and Probationary Firefighter Anne Sullivan, 24, who graduated from the department’s training academy in April.

Jeff Caynon, president of the Houston Professional Fire Fighters Association, said the victims included three men and one woman.

“Houston firefighters mourn the loss of our three brothers and our sister and will forever honor their sacrifices,” Caynon said. “This tragedy underscores the inherent dangers of our profession.”

Officials said the five injured firefighters likely would remain hospitalized for at least the night.

The blaze broke out just after noon at a restaurant and bar at the motel, then quickly spread to the section of the building housing the motel. About 150 firefighters responded and were able to get it under control within about two hours.

Front desk clerk Martha Lopez told the Houston Chronicle that a restaurant employee ran into the hotel saying a fire had started in the restaurant. The two began knocking on doors and windows telling guests to get out of the hotel. Lopez had 45 registered guests at the time.

Sammy Sewell, who had been staying at the hotel, said he walked out of his room and heard yelling. He said he turned a corner, saw three women screaming and running at him down a hallway. Then he heard three blasts.

“Next thing you know, it was ‘boom!’ It scared the crap out of me. I mean, it sounded like a cannon going off. That’s how loud it was,” Sewell told the newspaper. “I could have sworn it picked this building up and put it back down.”