Customs Service officials said yesterday that, for the second Friday in a row, they seized cocaine form a passenger at Dulles International Airport who arrived aboard Braniff International Flight 974, which originates in La Paz, Bolivia.

Officers said they discovered 3.2 pounds of cocaine taped to the legs of Alaine Joseph Marcel Belzile, 29, of Quebec City, Canada, shortly after a sniffer dog alerted them to the likelihood that the drug had been aboard the plane.

The weekly Braniff flight, which has an intermediate stop in Lima, Peru, is one of the few direct flights to the Washington area from South America. It has been dubbed the "cocaine express" by law enforcement officers because of the number of drug smugglers arrested on it. Last week customs officers siezed almost 12 pounds of cocaine from passengers on the same flight.

Customs Service spokesman Jim Mahon said yesterday that sniffer dogs are frequently run through planes coming from "high-risk areas" like Columbia, Bolivia and Peru. After a dog sniffed out the plane's seating area yesterday, an agent alerted officers in an inspection area that a drug suspect was coming through.

Mahon said the agents saw "bulges on his [Belzile's] legs where they shouldn't be" and searched Blezile, who was ticketed for J. F. Kennedy International Airport in New York.

The Canadian was turned over to the Drug Enforcement Administration, which charged with him with smuggling. He was ordered held under a $100,000 bond after a hearing in Alexandria.

Officials said the cocaine seized yesterday had an estimated retail value of $775,000.