A California man was killed and another man injured yesterday in a fire that spread quickly in a research laboratory in Prince William County where solid fuel propellant samples were being prepared.

Leon H. Cassutt, 59, of Newport Beach, a technician for Aerospace Corp., died after being burned in what officials called a "rapid fire" at the Atlantic Research Corp. facility in Gainesville.

Lt. Desmond McCallum of the Prince William Fire Marshal's Office said Cassutt died at noon at Prince William Hospital in Manassas.

The injured man was identified as James Hunt, 53, an employe of Vought Corp. in Irving, Tex., who was also working at the facility. He was taken to the hospital, treated for smoke inhalation and released, McCallum said.

Officials said the two did not flee immediately after what McCallum described as a "glow" occurred about 10:15 a.m. while a worker was handling classified solid fuel propellants.

The worker was quoted as shouting, "There's a fire, get out."

About 10 people fled "at a full gallop" from the lab at the end of a building, described as a 35-by-60 foot single-story corrugated steel on concrete structure with breakaway walls, McCallum said.

But Cassutt and Hunt were working in another small lab about 40 feet away from where the fire started and apparently didn't hear the warning, McCallum said.

Hunt said later that "all he heard was a commotion outside," McCallum said.

While Hunt was able to get out of the building, Cassutt moved in the direction of the fire, either in the confusion or to alert others, McCallum said. Cassutt was found next to an exit door.

"This is probably the worst incident we've ever had," said Bill Cook, manager of human resources at the Atlantic Research facility at 7511 Wellington Rd.

An investigation committee has been appointed to determine the cause of the blaze, he said.

An autopsy was being performed to determine the cause of Cassutt's death, authorities said.

Atlantic Research, headquartered in Alexandria, is a major developer and producer of solid propellant rocket motors and gas generators. Cook said the company also is involved in radar and other defense work.

Cook said he could not provide a damage estimate or details about the Prince William laboratory, one of the company's newer ones in its technology development cluster.

"We do a lot of military defense work here," he said. He said the facility, called the Pine Ridge Plant, employs more than 800 people.

The 420-acre facility, covers a large wooded area for safety reasons, he said.

A large blue and green banner stretched across one of the entrances to the plant yesterday: "Put Your Emphasis on Safety Today and Every Day."