Four firefighters died battling a five-alarm blaze that ripped through a large motel on a busy highway in southwest Houston on Friday, the authorities said. The Houston Fire Department said it was the single deadliest day in department history.

Five other firefighters were injured and taken to hospitals, where they were being treated for heat exhaustion and critical injuries, the department said.

The fire began shortly after noon at Bhojan, an Indian restaurant, according to a statement released by the Fire Department, and soon engulfed the adjacent Southwest Inn, a motel on a stretch of U.S. Route 59 called the Southwest Freeway.

Towering flames leapt into the sky, and dark smoke hung heavily over the building, whose front section appeared to have collapsed, according to footage broadcast by a Fox station in Houston.