FBI agents, armed with grand jury subpoenas and assisted by D.C. police officials, searched the police department's 4th District vice office yesterday, marking what sources said was the culmination of an FBI undercover investigation into allegations that some narcotics officers were skimming drugs and money.

A half-dozen agents arrived at 4th District headquarters on upper Georgia Avenue NW about 3:15 p.m. and began sifting through police records for warrants, affidavits, arrest reports and other documents sought by a federal grand jury. Some D.C. police officers secretly cooperated with the FBI in the investigation without the knowledge of their superiors, sources said.

The Washington Post also has learned that in a separate and substantially broader federal probe, authorities are seeking to determine the extent of relationships between a major drug distribution network and some police officers and city officials.

In the skimming inquiry, The Post reported two weeks ago that the FBI was investigating allegations of corruption in the enforcement of drug laws by the D.C. police department, specifically an alleged pattern of police officers personally profiting from their handling of drug trafficking cases.

The FBI is focusing on allegations that four or five officers kept drugs and money taken during narcotics raids for their own use, sources said. They said authorities are also investigating whether the officers used the confiscated drugs and money to pay their informants.

Sources said the FBI is probing allegations that a small group of officers pooled the drugs and money from several searches and then split the proceeds. The FBI also has been looking into allegations that departmental investigations of misconduct, including skimming, have been covered up.

Sources said yesterday that the search was conducted in conjunction with at least four officials from the police department's Internal Affairs Division, after a meeting between Timothy J. Reardon, principal assistant U.S. attorney, and Police Chief Maurice T. Turner Jr.

Turner said during the meeting that his department would comply fully with the subpoenas and provide any documents requested, according to sources.

The FBI, the U.S. attorney's office and the police department would not comment yesterday on the search or the two investigations.

The police corruption probe is one of several investigations by three grand juries into the awarding of numerous city contracts, possible obstruction of justice by associates of Mayor Marion Barry and expenditures from the mayor's office accounts.

The FBI probe of alleged police wrongdoing, the first such undercover inquiry in 30 years in the District, produced an unusual scene at 4th District headquarters yesterday.

As agents milled in and out of Room 229 -- the 40-by-30-foot vice squad room -- yesterday evening, Lt. Winslow McGill, the vice commander, paced the second-floor hallway. Two agents could be seen toting a large box sealed with white tape embossed in red letters that said "evidence."

Another man in plainclothes carried a large, self-sealing plastic bag stuffed with files, loose papers and long, thin notebooks such as those used by police investigators and officers. Another investigator carried a plastic bag with light green files.

In a neighboring office, police officers gathered around a television set, turning up the volume when the early news came on. "We have to learn about this from the news," said one.

About five hours after they arrived, FBI agents and police officials loaded at least a half-dozen large boxes into a police van. In an apparent effort to avoid news photographers and camera crews gathered in front, the van was backed into a covered loading dock adjacent to the building. Then the van and several unmarked police cars sped north on Georgia Avenue.

Sources said the FBI's police investigation is limited to the 4th District, although there have been similar allegations of skimming in the 3rd District near downtown, the 7th District in far Southeast and the narcotics division at police headquarters, 300 Indiana Ave. NW.

The subpoenas served yesterday pertained to drug investigations handled by two 4th District vice officers, according to sources.

The 4th District serves the upper reaches of Northwest and Northeast Washington and is bounded by Rock Creek on the west and by Harvard Street, Michigan Avenue, the Baltimore & Ohio railroad tracks and Gallatin Street on the south and east. It includes some of the city's most notorious open-air drug corridors as well as the nightclubs and bars that line Georgia Avenue.

According to law enforcement sources, nearly a third of the narcotics search warrants in the District this year have been executed by the 4th District vice squad.

Between January and September, a total of 927 narcotics search warrants were filed in D.C. Superior Court or U.S. District Court, including 26 by the FBI, the Drug Enforcement Administration and the U.S. Park Police, and 10 by "other" law enforcement agencies, the sources said.

During that period, 891 narcotics search warrants were executed by D.C. police and, of those, 303 were executed by the 4th District, the sources said. That is more than twice the number of warrants executed in the 7th District, where officials have said the highest number of drug-related arrests are made.

According to sources, the FBI investigation is focusing on drug arrests and raids in which the affidavits in support of the warrants indicated that officers might recover large amounts of drugs and money, but in which only small amounts were recorded on the 4th District's property books.

In recent months, sources said, FBI agents have reviewed scores of warrants issued to 4th District vice officers and have interviewed D.C. police officers who participated in the searches, as well as defendants and suspects in many of the drug cases.

The FBI is also trying to determine whether fraudulent information was submitted as part of the affidavits used to obtain some of the warrants, according to sources.

In some instances, sources said, officers allegedly said in their affidavits that they had information showing that drugs were being used or sold at a certain address when, in fact, they did not have such information.

The FBI is also investigating incidents in which some officers executed search warrants after the deadline imposed by the courts had expired, but allegedly claimed to the courts that the searches were conducted properly.

Search warrants issued by D.C. Superior Court and U.S. District Court are issued for specific locations, usually with a 10-day time limit, after officials have shown that they have probable cause to believe that a crime is being committed.

There also are allegations that 4th District officers have supplied drugs to their informants before the informants were sent to make controlled drug buys from dealers, sources said.

The sources said the officers have claimed in their subsequent affidavits that the informants actually purchased the drugs, enabling the officers to obtain warrants for which they had no probable cause.

One 4th District vice officer has been identified in court papers filed on behalf of an alleged drug dealer.

According to the papers filed by lawyer Allan M. Palmer, who represents Anthony B. Fultz, 4th District Officer Shelton D. Roberts stole more than $1,000 from Fultz during a raid on June 16.

Roberts, 40, a 17-year department veteran, was one of the officers who searched Fultz's home at 490 Taylor St. NE and reported that only $24 had been seized.

In the court papers, Palmer said he had learned that an FBI agent had interviewed at least one other drug case defendant who claimed Roberts "stole money from his premises during execution of a search warrant."

Fultz was indicted July 16 by a federal grand jury on charges of possessing cocaine and heroin with the intention of distributing the drugs, and possession of drug paraphernalia and marijuana.

Sources said the FBI is looking into instances in which more than $5,000 was allegedly stolen.

According to sources, nearly half of the search warrants issued to 4th District police officers were executed by Roberts.

After The Post reported the FBI investigation, Chief Turner vowed that "no blue veil" shields "wrongdoers within our own ranks" and that the department conducted "vigorous investigations of police transgressions."

Turner, who at the time said he knew nothing of the FBI investigation, criticized "vague allegations of corruption" published by The Post and said the story was "unsubstantiated."

Sources said it is highly unusual for a police chief not to be informed of a federal investigation of officers in his department.

The sources said the top-ranking police officers are usually notified, unless there are indications that previous wrongdoing has been covered up.

A high-ranking police official said yesterday that the incident showed that authorities realized that "part of the dilemma is that we work for the executive and {they} don't want us telling the mayor" about any investigations.

He said that relations between the FBI and the police department have been good in the past, but that the federal authorities have "damaged it tremendously. There's a great deal of anger."Staff writers Victoria Churchville and Sharon LaFraniere contributed to this report.