Two men who were arrested in connection with one of the largest seizures of cocaine in the District failed to appear at a U.S. District Court hearing yesterday after they posted bond and were released from custody less than 10 hours after their arrests, law enforcement officials reported.

U.S. District Court Magistrate Patrick J. Attridge issued bench warrants for the arrests of Larry Blackwell, 35, and Torrence D. Owens, 36, each of whom was charged Wednesday with two federal felony narcotics counts, conspiracy to distribute heroin and conspiracy to distribute cocaine, after D.C. police seized drugs with a street value of about $2 million from an apartment at 4660 Martin Luther King Ave. SW, the officials said.

Blackwell, of 11907 Autumn Wood La., Fort Washington, and Owens, of 210 Seventh St. SE, were released about 3 a.m. yesterday from the central cell block at D.C. police headquarters after a $5,000 "station-house" bond was posted for each, Assistant U.S. Attorney John Finnegan said.

Blackwell, who a court source said is on unsupervised probation for making a false statement on his passport, and Owens remained at large late last night.

"It is not extraordinary for them to have made a station-house bond," a bond that, for some offenses, is preset, Finnegan said.

Other law enforcement officials said, however, that the incident called into question procedures for station-house bonds and suggested that there should be a more thorough screening process before suspects are released without a hearing.

Assistant U.S. Attorney Thomas E. Roberts said that there are procedures by which police can prevent someone from being freed on a station-house bond. He said that his office, if aware that police want to hold someone, can call the cell block and ask that a suspect not be released or request that a magistrate order that a person not be freed.

"It's not the police's fault that they didn't know this," Roberts said, because it is "very rare . . . that someone is about to post bond and police want them held."

Blackwell and Owens were arrested after police executed a D.C. Superior Court search warrant at a fifth-floor apartment and found what they described as a major drug distribution business and narcotics packaging plant. The search came about 3 p.m. Wednesday after workmen went to the apartment to fix a water leak and discovered a large quantity of drugs and drug paraphernalia in an otherwise empty apartment. Police said they seized more than seven pounds of nearly pure cocaine and a quarter-pound of uncut heroin.

Blackwell and Owens were walking down a hallway toward the apartment about 6 p.m. and were arrested when they tried to run from the scene, police said. Bondsman Jesse L. Jones said he was contacted by a member of "their family," and that a friend of Blackwell and Owens paid him the standard 10 percent amount, or $500 each, to arrange for the bonds. He said the money was given to him in mostly $10 and $20 bills.

About 9 a.m. yesterday, Blackwell and Owens went to Magistrate Attridge's chambers but were told that their presentment hearing -- when their bond would be reviewed and a hearing date set -- was not until 1:45 p.m., the officials said.

They said that the men did not return, and Attridge issued bench warrants for their arrests about 2:30 for failure to appear. The men were at large last night, police said.

One veteran police official who was involved in the arrests said, "With the money they have . . . I'll be really surprised if we find them in the area."

Lt. Roger Chapman, watch commander at the 7th District, said a task force that included D.C. police, the federal Drug Enforcement Administration and the Federal Bureau of Investigation was organized last night to search for Blackwell and Owens.

"The task force is working through the night, on some leads, but I cannot say whether they are close to an arrest or not," Chapman said.

Police sources said yesterday that the apartment where the drugs were seized appeared to be a drug packaging plant where narcotic dealers had developed a scheme to "rip off" other dealers.

According to these sources, the dealers at the apartment purchased bricks of nearly pure cocaine and heroin, broke the bricks up and diluted them with "filler" ingredients, then made new bricks and marketed them as pure narcotics.

Besides a drug press used to make bricks and the mass quantities of heroin and cocaine that were seized, police said, 750 small bags of cocaine that were ready for street sale were also confiscated, in addition to two telephone pagers, $2,700 cash, face masks, gloves, numerous scales, measuring spoons, sifters and large quantities of mannitol, inositol, lactose and quinine, substances that are frequently mixed with narcotics.