The Houston Fire Department lost four firefighters engaged in rescue operations in a blazing Houston motel and restaurant on Friday, when part of the structure caved in on them, authorities said.

The fire, dubbed the deadliest so far for the department, which has been in existence for more than a century, injured at least another five firefighters, AP reported.

“We had an early and quick catastrophic failure of the roof,” Fire Chief Terry Garrison told the Houston Chronicle.  “There's no way that I would have anticipated that we would lose four firefighters. I want to tell the residents of Houston their firefighters acted absolutely courageously today, that there was probably a dozen acts of heroism on that scene.”

The Southwest Inn, situated along U.S. Highway 59, was ablaze Friday afternoon, with thick black smoke rolling upward and enveloping the area, as responders tried to put out the fire.

The blaze broke out at a restaurant and bar at the motel and spread quickly to the rest of the building. Guests who were inside the motel were warned of the fire and bolted to safety.

About 150 firefighters reached the scene and brought the fire under control within a couple of hours. Three firefighters died at the scene, while the fourth died at a hospital, AP reported, citing the mayor’s office.

Garrison said there were no missing persons and authorities were yet to ascertain the cause of the fire.

Friday’s loss of life was the single worst for the department, which was established in 1895 and has lost 64 employees so far in fire accidents.

“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 was quoted as saying by AP. “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; Engineer Operator Robert Bebee, 41; Firefighter Robert Garner, 29; and Probationary Firefighter Anne Sullivan, 24, AP reported.