Mark Larson was driving home from work in August when a back pain he'd noticed earlier in the day suddenly became worse, "like someone was shoving a knife underneath my shoulder blades."

He pulled into the parking lot of his Northwest Washington apartment and discovered that his legs were paralyzed. Two friends carried him up the stairs to his third-floor flat, where he lay down on the floor while the D.C. Fire Department was called.

Two emergency medical technicians arrived and, according to Larson, examined him and told him the problem was "mental," that he could walk if he wanted to. Larson said four friends carried him downstairs after the EMTs refused to do so.

The ambulance attendants took him to George Washington University Medical Center, where doctors determined he had a blood clot near his spine.

Now, after an operation and a six-week, $50,000 stay in the hospital, Larson, his friends and family have filed a complaint against the EMTs who took him to the hospital.

The fire department has begun an investigation of the Aug. 13 incident and the two EMTs involved have been given administrative duties pending the outcome, a spokesman said.

"I was very, very angry," said Larson, 27. "When they [the EMTs] were telling me it was all psychosomatic, I felt like . . . 'how dare you stand there and tell me I'm mentally disturbed.' "

An expert in prehospital care who reviewed Larson's case said his treatment before arriving at the hospital "most probably had no bearing on his final outcome." Larson has regained most of the use of his legs but has lost control of his bladder. He now goes to physical therapy and is uncertain when he will return to work.

Fire department spokesman Ray Alfred said that if Larson's allegations prove accurate, the EMTs' actions were "totally unprofessional."

One of the EMTs, Warren A. Bucksell, a three-year member of the ambulance division, said he would not comment on the incident. His partner, Fred Mobley, also a three-year employe, could not be reached for comment.

Alfred said that a person does not have to be carried on a stretcher if the ambulance attendants believe it will "not jeopardize or exacerbate the condition of the patient . . . . We can't take away all the judgment, but we tell the guys [that] if there's any question, get a stetcher and roll him out."

According to a physician who treated Larson in the emergency room, doctors discovered he was suffering from acute paraplegia brought on by a blood clot near his spine that interfered with the spinal cord's function.

The physician said the blood clot was removed in an operation that night.

Larson, head of visual displays at Montgomery Mall's Hecht's department store, said he noticed the back pain Aug. 13, after moving a large urn at work.

After he was carried up to his apartment, his roommate, Curtis Yee, called another friend, a nurse who was having dinner with a physician, according to Yee's statement to the fire department.

Both the nurse and physician said that Larson should be taken by ambulance to a hospital and stressed that he be "moved by a stretcher," according to the statement.

According to Yee's statement and a statement by Larson's aunt, Vietta Dowd, Bucksell told Larson the problem was "mental." The EMTs then unsuccessfully tried to stand him up to walk, according to Dowd's and Yee's statements.

According to Dowd's statement, Bucksell said that the ambulance was not equipped with a stretcher, and that Larson would have to walk downstairs.

When Yee asked if the EMTs would carry Larson, his statement says, "Mr. Bucksell answered by stating that he was 40 years old and had no intention to break his own back by carrying Mr. Larson down three flights of stairs."