Montgomery County police said yesterday they are searching for the killer of a 32-year-old engineer who was stabbed to death in his Gaithersburg apartment over the weekend.

Nelson Clay Waters, who lived alone in the one-bedroom apartment, suffered multiple stab wounds in an incident that probably occurred late Friday night or early Saturday morning, according to police spokesman Harry E. Geehreng.

When Waters failed to appear at work Monday at Bechtel, an engineering firm in Gaithersburg, and when his colleagues couldn't reach him at home by telephone, they notified police, Geehreng said.

Police then went to the Diamond Farms Condominiums in Gaithersburg where Waters lived, Geehreng said. Manager Jeanne Smarte said she provided police with a key to the unit that Waters had rented from its owner for the past year. Smarte would not say who owns the ground-level unit where Waters lived in the garden-style complex, which has 540 units on 33 acres.

Geehreng said Waters apparently was stabbed in the bedroom and then staggered into the living room where investigators found his body at about 1:30 p.m. Monday. The telephone receiver was off the hook when police entered the unit, so anyone trying to call Waters would have gotten a busy signal, Geehreng said.

A Bechtel official said Waters worked for the company in Gaithersburg for four years as a cost engineer responsible for accumulating cost data on construction and engineering projects.