A U.S. grand jury in Boston is investigating several Virginia apple growers as part of a larger East Coast probe of alleged illegal payments to thousands of Jamaican migrant workers, the U.S. Attorney's office in Boston said yesterday.

The Frederick County Fruitgrowers Association of Winchester, Va., confirmed yesterday that three of its members have been questioned and the association's transportation records subpoenaed by the Boston panel.

The investigation is the latest development in a lengthy controversy involving the growers' hiring practices, which have been criticized as unfairly favoring foreign pickers over American citizens, including workers from Puerto Rico.

Delmer Robinson, chairman of the association's labor committee, said the grand jury was concerned that some growers were illegally advancing the Jamaican workers money for travel to East Coast apple orchards.

Growers are permitted to give such advances under Labor Department regulations, but only if the funds are made available to all migrant workers, domestic as well as foreign.

A Boston newspaper recently quoted Labor Department sources as saying Jamaican workers receive travel advances not offered to U.S. workers because growers frind that Jamaicans work harder, and for lower wages, than their domestic counterparts. The growers also do not have to make Social Security or unemployment compensation contributions for foreign laborers, the sources reportedly said.

Labor officials in Washington yesterday refused to confirm or deny the published reports, noting that the grand jury's investigation is secret.

An attempt by the Labor Department to have 1,000 Puerto Rican pickers employed in Virginia orchards last year ended in near-chaos after the program broke down in a maze of red tape and a bitter dispute between grower and government. More than 550 of the workers went home less than two weeks after their arrival.

Several East Coast growers said at the time they found the Puerto Ricans less reliable and hard-working than the Jamaicans they had been importing for decades under a special exception to U.S. immigration laws.

Under the exception, employers were allowed to import foreign workers if not enough willing and able U.S. citizens could be found to do the work.

Robinson of the Fruitgrowers Association said yesterday that Jamaican banks currently loan money to workers destined for East Coast orchards with a guarantee of U.S. jobs as security.

In a related development, Puerto Rico's labor secretary yesterday turned down a U.S. government plan to help import 600 Puerto Rican laborers to harvest fruit in Virginia and other East Coast states.

According to Judy Sorum, a special assistant to U.S. Labor Secretary Ray Marshall, the department had offered to spend $230,000 to provide transportation costs and a two-day orientation program for the workers.

Sorum said Secretary Carlos Quiros objected to requirements for documentation for the workers. "The documentation is to protect workers from unscrupulous labor contractors," Sorum said, "and to ascertain that workers are qualified to work in the U.S."

Sorum said Quiros also felt the plan did not give the Puerto Rican government enough control over where the workers were sent and did not allow enough time to recruit workers effectively.