Seven small Korean-owned businesses in upper Northwest Washington that have been firebombed in the last 10 months may be the victims of extortion by other Koreans, according to sources familiar with a joint D.C. police and federal investigation of the fires.

Though police and members of the District's Korean community originally said that they thought the businesses were bombed by blacks who resented Korean-owned businesses in their neighborhood, investigators now believe that the fires were started by other Koreans.

"I would strongly suspect that there is some kind of organized criminal activity" behind the bombings, a source close to the investigation said. The motive, he said, appears to be "to gather power within the ethnic group and to extort money."

Sources said that there is no hard evidence to tie specific persons or groups of persons to the incidents. However, they said that, because of the pattern of the firebombings, investigators believe that a Korean gang, styled after those in New York and Los Angeles, may be extorting money from the businesses.

The sources said that investigators also believe loosely organized Korean financial groups, called "kehs" (pronounced kays), may have lent money to the businesses, and that the firebombings are meant as a warning to repay the loans in a timely fashion.

The seven Korean-owned businesses that have been firebombed are all located within two miles of each other in upper Northwest. The first bombing occurred Dec. 12, 1984, at Rocket Liquors, 900 Kennedy St. NW, and the most recent bombing was Aug. 29 at the Korea Times Newspaper, 4817 Georgia Ave. NW.

Owners and managers of the businesses that have been firebombed said that, to their knowledge, there are no Korean gangs in the District. All denied any involvement with kehs. While some said it was possible that kehs were behind the bombings, most discounted the idea. Some suggested that the bombings are racially motivated.

"At one point there were rumors of friction between blacks and Koreans as a result of Koreans not hiring blacks in their businesses," said D.C. police Inspector Richard Pennington, the police department's liaison officer with the city's Korean community.

However, he said, after more than 2,500 interviews with area residents, investigators have concluded that racial problems between blacks and Koreans are "not as bad as we thought."

"We're looking at the possibility of extortion, we're looking at everything," he said, including the roles of gangs and kehs.

A source familiar with the investigation by D.C. police, which in May formed a task force to investigate the bombings, and the Treasury Department's Bureau of Alcohol, Tobacco and Firearms said that the firebombings are "a message device. Somebody is trying to tell someone something."

The source said that firebombings are "a very common tactic" used to extort money from Korean businesses in Los Angeles, which has a powerful gang called the KK (for Korean Killers) and in New York, where a gang called Korean Power is located.

"I'm not saying that our problem here is related to them," the source said, "but we find the same pattern of offenses occurring against the same kind of businesses. The same method, the same devices, the whole nine yards."

Inspector Pennington said that police "believe that the person or persons involved are responsible for all seven" firebombings.

According to police, all the arsons fit a pattern. Each was aimed at a Korean-owned business and was committed early in the morning.

All were done with a small container of flammable liquid that had some kind of timing device to delay the explosion, and all the containers were placed against a door. In every bombing except one, damage was primarily to the outside of the buildings and was limited to permit most of the businesses to reopen within 24 hours.

"Based on our investigation so far, it appears the culprits or people responsible for committing these arsons don't want to totally destroy these businesses," Pennington said. "If they wanted to burn these people out, they could."

Sources familiar with the investigation said that the relatively minor damage received by the businesses also indicates that the firebombings are not racially motivated attacks aimed at forcing Korean firms from the predominantly black neighborhood.

It appears, the sources said, that the arsonists do not want the businesses to suffer prolonged financial hardship. If the arsonists were financial lenders, the sources said, it would not make sense for them to take away a business' source of income.

Except for the Korea Times, all of the businesses that have been firebombed have English names, one source noted, leading investigators to conclude that the arsonists are familiar with Korean establishments -- which comprise about 60 percent of Asian-owned businesses in that area of the city -- and have some way of distingushing them from businesses owned by other Asians.

Sources also said that, if there were general hostility between blacks and Koreans, it probably would show up on a city-wide scale.

Sources said that a July 4 firebombing at a Chinese-owned business, General Commodities Co., 125 Missouri Ave. NW, may have been a copycat incident or an attempt to lead police investigators astray. A source said that the incident happened soon after investigators started to inquire about gangs and kehs.

In Korea, kehs are generally set up between family members or close friends to give the participants a windfall of cash. For instance, a keh might be formed by 12 persons, each of whom makes a monthly payment of $100 into a kitty that then goes to one of the members. Although each person has a steady outflow of $100 every month, once a year the person would be entitled to a $1,200 windfall for investment.

Kehs are based on trust and human relationships, are not documented and are not legally enforceable, according to Koreans familiar with how they work.

"There are many kehs in greater Washington, D.C.," said Taehee Yoo, owner of the Korea Times, who said he doubted kehs were behind the bombings but "couldn't rule it out."

"It's true when a business starts, it's hard to get a down payment, and they owners can get a benefit from kehs," Yoo said. If a person is the first to receive the kitty and then can't keep up with monthly payments, he said, "then you got trouble. There are no papers. Just trust each other. Sometimes a guy can't afford to pay it."

Klasha Han, manager of Leon's Cleaners at 300 Missouri Ave. NW, which was firebombed Feb. 16, said that Koreans were "absolutely not" behind the bombings and that police have developed "theories without substance."

"I wish somebody would come up and ask for money," Han said. "Then I'd know what it is" that led to the fire.

Il Ho Kim, treasurer of the Korean Businessman's Association of the Washington Metropolitan Area, said he was "strongly opposed" to theories that implied Koreans were behind the firebombings.

"In my opinion, there is no possibility, not even one percent" that gangs or kehs are behind the bombings, said Kim, who estimated that there are 1,000 Korean-owned businesses in the District. He attributed the incidents to "hostility against Koreans . . . . Whenever I join some black community meeting, I can feel some hostility exists there."