New York and Miami drug dealers, many of them Jamaican, have recently moved into Washington, D.C. police sources say, and several rival groups are battling to control the large open-air drug market in the Mayfair Mansions-Paradise Manor area of Northeast.

In what prosecutors and law enforcement officials say is the first major influx of dealers from other states into the Washington area, eight major narcotics distribution cases involving at least 20 New York and Miami residents have been brought to the U.S. District Court here during the past two months.

Many of the New York residents charged here are from the same Brooklyn neighborhood, and authorities think the dealers may be involved in a systematic attempt to capture part of Washington's lucrative drug market, especially the growing demand for "crack," a cocaine derivative.

"Because of the availability of cocaine and crack in New York, a port city, prices are low there," said Assistant U.S. Attorney John F. Finnegan. "In Washington, dealers can get $30 for what sells at $15 in New York."

Court records show that many of the New York and Miami residents are Jamaican nationals, some of whom are in the United States illegally.

The Jamaican drug dealers are heavily armed, often with sophisticated automatic weapons and machine guns, said a police source. There have been at least six drug-related homicides linked to Jamaican drug dealers in the past 10 months, but police say there are many other shooting incidents that aren't reported to authorities.

"People just show up at hospitals and say they were shot accidentally," a police officer said.

Police believe that some of the Jamaicans are linked to a drug distribution network that has ties to other major cities, including Kansas City, Mo.; Cleveland; Baltimore, and several cities in Texas. "Jamaicans are coming here in droves," said a police source. "Washington is the new frontier for them."

Police sources say that the largest concentration of Jamaican drug dealers operates from the Mayfair Mansions and Paradise Manor apartments in Northeast Washington, off Kenilworth Avenue, in what has developed over the past year into "one of the biggest open-air drug markets on the East Coast."

Police estimate that as many as 100 dealers operate in what they refer to as the "Mayfair market," with about 60 percent of them belonging to two or three loose-knit Jamaican organizations. Police sources say the success of those Jamaicans in the drug market here has attracted other New York and Miami dealers, who control the remainder of the Mayfair market.

Local drug dealers who once controlled the Mayfair market have been transformed into crews of holdup men who rob the out-of-town dealers and terrorize residents, according to D.C. police sources.

A Prince George's police detective, who asked not to be identified, reported a similar pattern, saying outsiders have moved in on outdoor drug markets in Landover and Langley Park since January.

Mayfair Mansions and Paradise Manor are separate large apartment complexes within a long horseshoe-shaped loop that backs up to the Kenilworth Aquatic Gardens. A long open courtyard runs through the center of the loop, and apartment buildings for the two complexes run perpendicular to the street and the courtyard. Parking lots are interspersed between the buildings and abut the courtyard.

Mayfair Mansions, a group of traditional style red-brick buildings, sits closer to Kenilworth Avenue than Paradise Manor, which is adjacent to the park. The buildings in Paradise Manor are more severe looking and have open breezeways that connect adjoining structures.

Drug sellers usually congregate along the center courtyard and inside the breezeways, turning the neighborhood into a giant "drug shopping center," complete with convenient parking, according to a drug enforcement detective, who asked not to be identified by name.

"The layout means that in any attempt to 'sweep' the area, the drug dealers have an upper hand," explained the detective.

Officials said that management of the two complexes have cooperated with police in doing "everything they can to help."

Ten days ago, about 200 persons gathered outside a building while police officers executed a search warrant inside and arrested three persons. Authorities called in several additional police units and a helicopter to disperse the crowd after an anonymous caller warned that dealers planned to attack the officers when they emerged from the building.

Court papers and interviews show that many of the out-of-town drug dealers follow a similar pattern when they come to Washington, first staying at a motel until they find a local resident in whose apartment they can set up their operation.

Usually the dealers locate a drug user, often an unemployed woman receiving welfare whose drug habit exceeds her ability to pay. The dealers supply the resident with drugs in exchange for the use of the apartment.

Each of the dealers, who are generally in their early twenties, employs runners who sell drugs in the open courtyard while the dealers sell from inside the buildings.