Exploding oxygen tanks fueled a four-alarm fire at a Crofton office building yesterday afternoon that sent employees fleeing and caused an estimated $2 million in damage.

No one was injured in the blaze, which began in a medical supply office and took 85 firefighters about an hour and a half to bring under control, fire officials said.

"After a few pops, a huge puff of black smoke filled the air," said Charles Mitchell, who was eating lunch at a nearby restaurant when the fire began. "It seemed like the building caught on fire immediately."

The fire, which destroyed the west wing of the U-shaped office building in the 1600 block of Crofton Blvd., left four businesses without some of their office suites, said Lt. Frank Fennell, a spokesman for the Anne Arundel County Fire Department.

One of the owners of American Home Medical, a business that repackages oxygen containers for home use, was filling an oxygen bottle shortly before noon when he heard the crackle of a fire behind him, Fennell said.

Employees at nearby businesses said the man tried to extinguish the fire but called 911 when it quickly grew out of control.

"The firefighters rushed right in there, not knowing whether it was chemicals or what," said Sue Robinson, who watched the event unfold from her doctor's office across a parking lot.

Firefighters pulled back when the explosions began and attacked it from the outside until it was brought under control at 1:35 p.m., Fennell said.

Eastern winds whipped a blanket of smoke through much of Crofton, limiting visibility on busy Route 3 in the western part of the county. Southbound traffic, confined to one lane to accommodate emergency crews, crawled for hours.

Stunned tenants stood in nearby parking lots to watch as firefighters from Anne Arundel and Prince George's counties, Annapolis and the Naval Academy battled wind to douse the fire.

About 25 employees in 10 businesses dashed out of their offices minutes before flames swallowed the building's entire western wing, onlookers and fire officials said.

The local office for Stanley Steemer, which is adjacent to the suite where the fire began, was intact last night. But employees said they barely made it out.

"We took what we could and ran," employee Stephanie Snead said. "Flames were just rolling out."

Across the parking lot, patients and staff at a doctor's office watched as the building appeared to explode.

"It scared the hell out of me," said 82-year-old Robert Rawes, who arrived for an 11 a.m. checkup and ended up stuck at the doctor's office until 2 p.m.

Rawes and other onlookers were trapped in parking lots while firefighters battled the fire.

"Curiosity kind of killed me," said Aaron Nickas, who was blocked in a parking lot by fire equipment after he drove over to see where the thick smoke was coming from.

According to property records, Warren and Martha Halle own the office building, which has an assessed value of $1.23 million and is divided into 16 office suites. The Halles could not be reached for comment last night.

Snead, still trembling hours after her close encounter, said she and her fellow employees worried that they would be displaced during the busiest carpet-cleaning season -- the holidays.

"We just want to get back in there," she said, glancing at the smoldering building, "and get back to work."

Sun staff writer Rona Kobell contributed to this article.