Zaire gave $1.3 million to seven close associates of President Mobutu Sese Seko in what U.S. congressional investigators described yesterday as an unauthorized use of funds generated by the American Food for Peace Program.

The investigators also discovered a $5 million deficit in the fund that is created by the sale of American rice at a subsidized price in an effort to combat chronic malnutrition in Zaire. Proceeds from such sales are not returned to the United States but are instead kept in Zaire for use in development projects approved by the U.S. Agency for International Development.

Charles Hylander, deputy director of the General Accounting Office's international division, told a subcommittee of the House Foreign Affairs Committee that there were other irregularities to indicate a "fair amount of corruption and black-marketeering" involved in the distribution of U.S. rice and other agricultural commodities in Zaire.

Hylander also said that Zaire was in violation of U.S. laws dealing with the use of military equipment, specifically C130 aircraft sold to Zaire under a subsidized program. He said planes were used to fly cobalt exports to Europe "weekly and on a scheduled basis." One aircraft is used full time by Mobutu while others occasionally transport "supplies with goods" to his presidential retreat in Gbadolite.

Officials would not disclose the names of Mobutu associates who received unauthorized counterpart funds, but after an official U.S. protest, they said Zaire had used a bookkeeping device to cover the $1.3 million without actually returning the money to the fund.

"If this is restitution then theft is honesty," said Rep. Stephen Solarz (D-N.Y.), chairman of the subcommittee on Africa that is conducting hearings on U.S. military and economic assistance to Zaire.

Since 1976, the United States has provided about $67 million worth of rice in these concessionary or subsidized sales to Zaire under the Food for Peace program. Another $7.3 million in food donations were sent to Zaire to counter a famine threat.

The U.S. investigators said 13 percent of all U.S. shipments is "lost" after reaching ports in Zaire and before it ever gets to the distributors.

"Nobody knows how much of the remaining 87 percent reaches the people" for whom it is intended, Hylander said.

"The great bulk is distributed to the military and other institutions," he continued, "and a significant portion of it is used for corrupt purposes."

In Daz Zaire, the report said, local legislators were permitted to buy rice in quantities large enough "to feed 9,000 people" for one year.

Hylander said that the investigators know of confirmed instances of U.S. food being used for currupt purposes. The U.S. Embassy had limited capability to monitor the food distribution process, he added, conceding that only three persons were involved in the monitoring last year.

The investigators, asked by Congress to look into charges of widespread government corruption in Zaire, said they could not assess the use of about 900 trucks and cars delivered to Zaire under the military assistance program. They said the Zairian military "could not readily tell us how many and what types of vehicles were currently in inventory, or their operating condition."

W. Haven North, deputy assistant AID administrator for Africa, disclosed that the U.S. Embassy in Kinshasa recommended last summer that the U.S. rice shipments be halted.

U.S. assistance to Zaire, especially the military program, has generated a controversy in Congress. Critics have charged that the Mobutu government will fall because of "its own corruption and inefficiency" and that Washington should not support an unpopular autocrat.

The $10 million annual military assistance is perceived as a symbol of U.S. backing for the Mobutu government.