CHARLESTON, S.C. -- Fire swept through a furniture warehouse, collapsing its roof and killing nine firefighters inside -- the nation's deadliest single disaster for firefighters since the Sept. 11, 2001, terror attacks.

"Nine brave, heroic, courageous firefighters of the city of Charleston have perished fighting fire in a most courageous and fearless manner, carrying out their duties," Charleston Mayor Joseph P. Riley said at a morning news conference. "To all of their loved ones, our heart goes out to them."

Two employees in the building were rescued from the blaze, which broke out about 7 p.m. Monday in the Sofa Super Store and warehouse, Riley said. One was rescued quickly, and firefighters punched a hole through a wall of the warehouse to reach the other, he said.

Firefighters, police officers and other rescue workers saluted as the firefighters' bodies were carried from the warehouse during the night.

"To lose nine is just a tragedy of immense proportions," Riley said. "To lose nine is just unbelievable."

The department has 237 firefighters in 19 companies located throughout the city of about 106,000.

The cause of the fire was under investigation, but Riley said arson was not suspected. He said the blaze apparently started in a storage area. He was unsure whether there were sprinklers in the building.

Fire chief Rusty Thomas said he lost nine of his best friends.

"They did exactly what they were trained to do," he said. "We got a long road ahead of us but we're going to stand tall. ... We're going to stand tall now and for years to come with the families, and we will never forget, just like 9-11, we will never forget."

It was the worst single incident to claim firefighters' lives since the Sept. 11 attacks, which killed 340 firefighters, two paramedics and a chaplain, according to the National Fire Protection Association. It was the deadliest fire in South Carolina since a 1979 blaze killed 11 people in the Lancaster County jail.

"These firefighters were true heroes who demonstrated great skill and courage. Their unwavering commitment to their neighbors and to the city of Charleston is an inspiration to all Americans," President Bush said in a statement issued in Washington.

Officials identified the victims Tuesday as Capt. William "Billy" Hutchinson, 48; Capt. Mike Benke, 49; Capt. Louis Mulkey, 34; Engineer Mark Kelsey, 40; Engineer Bradford "Brad" Baity, 37; Assistant Engineer Michael French, 27; Firefighter James "Earl" Drayton, 56; Firefighter Brandon Thompson, 27, and Firefighter Melven Champaign, 46.

Witnesses said the collapse of the roof threw debris over about two-dozen rescue workers. Onlookers were hit with flying ash.

"It was like a 30-foot tornado of flames," said Mark Hilton, who was struck in his eye.

Firefighters went to a nearby car dealership asking for towels and quickly got additional help, said salesman Daniel Shahid.

"The next thing you know, we were carrying hoses, directing traffic, everybody from the dealership," he said.

Shahid said he saw firefighters rescue four people from the building.

"They were struggling. They were covered in black soot. They looked scared out of their minds," Shahid said.

He later told CNN the roof collapsed too quickly for anyone to escape.

"It came from nowhere," he said. "It was a standing structure and five seconds later it was on the ground."

Riley called the firefighters heroes.

"This is a profession that we must never take for granted," the mayor said. "There's a fire raging and they go toward it."

Gov. Mark Sanford ordered state flags lowered to half staff. "These are truly some of South Carolina's bravest, who in this case made the ultimate sacrifice in the line of duty," he said.

Store owner Herb Goldstein said in a statement there were no words to express his sorrow.

"All of us at Sofa Super Store are devastated and heartbroken by this tragedy. Our thoughts and prayers go out to the families and loved ones of the heroic firefighters who lost their lives," he said.

He had owned the store for about 15 years, said his son, Jeff Goldstein.

In a small plaza next to the city's main fire house, notes and flowers were left at the base of a monument to firefighters Tuesday.

"Our thoughts and prayers are with all of you and your families. We are deeply saddened and want you all to know that we value your bravery and thank you for putting your lives on the line to keep us all safe. God bless you all," read one note.

The buildings are located on what residents here refer to as the "auto mile," a commercial strip of car dealers, body shops and stereo installers.