Two federal agencies have found "possible violations" of conflict-of-interest law by John R. McKean, chairman of the U.S. Postal Service Board of Governors, and William F. Bolger, the former postmaster general, according to documents released yesterday by Rep. William D. Ford (D-Mich.).

The findings have been referred to the Justice Department, according to officials of the General Accounting Office and the Office of Government Ethics.

The agencies investigated allegations that McKean, a California accountant, participated in the award of a $300,000 postal service contract to a San Francisco labor-law firm for which McKean has done accounting work.

The agencies also investigated reports that Bolger, who left his job Dec. 31, participated in last year's postal-rate deliberations while negotiating a possible job with the Direct Marketing Association, a mass-mailing group whose members would be affected by rate changes.

Ford, chairman of the House Post Office and Civil Service Committee, requested the investigations in September after reports were published in a postal union publication, the San Francisco Chronicle and The Wall Street Journal.

McKean and Bolger have denied any conflict of interest. Bolger repeated his denial yesterday while McKean said through a spokesman at his San Francisco firm yesterday that he has "no comment whatsoever" on the case.

"I would not have done any of this if I didn't think it was proper," Bolger said.

McKean's appointment to the part-time postal job has stirred controversy because McKean was appointed on Attorney General-designate Edwin Meese III's recommendation after Meese received a $60,000 loan arranged by McKean.

Bolger last June awarded a six-month contract to the law firm Littler, Mendelson, Fastiff and Tichy to assist the Postal Service in contract negotiations with its unions.

McKean, in an interview with the Chronicle in August, said he had asked Bolger to "take a look at" hiring the firm, and had "sat in" on a June 4, 1984, interview Bolger held with partners in the law firm.

The contract was awarded June 15, and McKean sent a letter dated that day to the Board of Governors stating that his firm had worked for the law firm and removing himself from "any decision" to hire them "to avoid even any appearance of a conflict of interest," the Chronicle said.

Yesterday Bolger said McKean "introduced me to the firm, but I don't recall any suggestion that I hire them. He just described them as . . . highly qualified."

The hiring of the law firm added controversy to postal negotiations last year because the American Postal Workers Union and the National Association of Letter Carriers, which initially disclosed McKean's link to the firm, said the law firm has a history of "union-busting." The unions had asked Ford to investigate the hiring.

Regarding his own case, Bolger said he disqualified himself last May from postal-rate proceedings because of his job negotiations with Direct Marketing Association prior to his planned retirement. Bolger ultimately did not take the job.