A Food and Drug Administration investigation has found that at least two cases of AIDS in the Washington area resulted from transfusions with blood that had been screened for the AIDS virus.

The finding is part of an FDA investigation into procedural deficiencies in American Red Cross blood services, including the now-defunct Washington chapter blood bank.

"Of the 75 cases reviewed so far, two have been associated with transfusions from donors who were later found to be infected," said Gerald V. Quinnan Jr., deputy director of the FDA's Center for Biologics, Evaluation and Research. "Seven more are under evaluaton, many of which are probably AIDS infections resulting from other causes {not from transfusions}."

Stephen H. Richards, senior vice president and general counsel for the American Red Cross, acknowledged that some of the transfusion-associated AIDS cases have occurred in the Washington area after blood tests to detect the AIDS virus began in March 1985. "It is our belief, though we can't be 100 percent sure, that the post-1985 incidents would have been in the window period."

The "window period" is the time between when a person is infected with the Human Immunodeficiency Virus that causes AIDS and when infection is revealed by a blood test that detects antibodies. It can take a few weeks or as long as 18 months for antibodies to appear.

"It is something that the test cannot pick up," Richards said. "It is not a procedural error. We have not found anything to indicate a post-March 1985 infection that was due to procedural, technical or computer errors."

As of last month, the Centers for Disease Control said it knew of about 11 cases of transfusion-associated AIDS nationwide since the blood test was licensed five years ago.