Houston ? Fire broke out in a six-story office building Wednesday, killing three people and injuring at least six, while many others inside climbed down to safety on ladders, fire officials said.

Houston firefighters go into the fifth floor of a six-story office building in Houston where a fire broke out Wednesday afternoon. Three people died and at least six were injured, fire officials said. The injured included at least three firefighters.

The fire broke out at the end of the business day. Flames shot out of the building’s top floors, and heavy smoke blanketed a nearby 10-lane freeway during the evening rush hour.

Television footage showed flames breaking through glass, and fire personnel guiding people down ladders.

Firefighters found the three bodies on the building’s fifth floor, District Fire Chief T.J. Dowdy said. Two bodies were found in the same office, and the other was nearby.

Three firefighters were injured, Dowdy said.

Four of the injured people were taken to Memorial Hermann-Texas Medical Center, where a spokesman said one was in critical condition, two in fair condition and another in good condition.

The fire is believed to have started in the offices of a medical supply company on the fifth floor. The fire stayed on the fifth and sixth floors, Dowdy said.

Jim Jimenez, owner of J Systems on the fourth floor, said he was in the atrium when he smelled smoke and then saw the fire. He left and saw the fire raging as he looked back, Jimenez said.

“It looked like the entire suite was on fire. It just took seconds,” he said.

Built in the early 1980s, the masonry and glass building is about 58,000 square feet. It is on the 610 Loop, a busy highway.