Firefighter Barbara (Sandy) Lee was struggling for her life yesterday after falling from a fire truck and under its back wheels during a routine run on a job that friends say was her "first love."

Lee, one of eight women firefighters among 513 in Prince George's County, was critically injured Tuesday night when she fell from the ladder truck as it rolled slowly down the long ramp at 8:25 p.m. from the department's Tuxedo-Cheverly station onto Tuxedo Road, a few miles north of the District line.

It is not clear yet what precipitated her fall, but yesterday the Potomac Senior High School graduate lay in critical condition at the Shock Trauma Center in Baltimore after undergoing five hours of surgery to repair massive internal and external injuries.

Capt. Jim Mundy, director of the fire department's communication office and a friend of Lee, calledfirefighting her life ambition. He described her as "intelligent, personable and a good firefighter" with excellent prospects for promotion.

Indeed, Lee's resume bears out her drive to be a good firefighter. At 19, the Laurel native was a volunteer at the Bladensburg station. At 23, she became one of the first women hired by the Prince George's County fire department. And three weeks ago, at age 26, Lee qualified to begin training for sergeant -- the first woman in the department's history to do so.

An investigation of the incident is under way, Mundy said, but no one appears to be at fault. There were four firefighters on the truck at the time and Lee was riding on the right side in an open area without abarrier. The truck, which weighs more than 16 tons, was moving at less than 10 mph down a dry ramp, according to Mundy, and no one noticed Lee's fall as the truck left the ramp until the back wheels rolled over her abdomen and legs and she screamed.

Lee was rushed by paramedics to Prince George's General Hospital, where her friends and coworkers kept a bedside vigil.

About 25 firefighters appeared immediately at the hospital after the accident was announced Tuesday evening and the response to a call for blood donations was overwhelming, Mundy said.

The alarm that started the fire truck rolling Tuesday night was triggered by a dramatic change in water pressure that set off the sprinkler system in a Bladensburg apartment building.