INDIANAPOLIS, AUG. 18 -- Pan American Sports Organization president Mario Vazquez Rana said today that the medical commission for the Pan Am Games has discovered the presence of a new drug masking the effects of anabolic steroids in "two or three" cases of athletes who have been drug-tested here.

Vazquez Rana said the new substance, Probenecid, is not on the list of drugs banned by the International Olympic Committee. For that reason, no action can be taken against the athletes found to have used it. Vazquez Rana declined to name the athletes or the countries.

Monday, Vazquez Rana announced that six athletes, including U.S. hammer throw silver medalist Bill Green, had tested positive for drug use. The athletes were disqualified and stripped of any medals.

Vazquez Rana said a study of the new substance would be made, and that the PASO executive committee probably would recommend to the IOC that it be banned from future competitions, including the 1988 Olympics in Calgary and Seoul.

"I cannot penalize someone or something that is not banned," Vazquez Rana said. "I will not make the athletes public and take their medals because I am not empowered to."

In a related matter, Vazquez Rana admitted today that not all medalists at the Games are being tested for drugs. How many athletes are being tested became an issue Monday when Vazquez Rana said that every medalist in every sport had been checked, contradicting statements made by Dr. Eduardo Henrique De Rose, president of the PASO medical commission.

De Rose has said that only about 1,000 of the 5,000 athletes here will be tested. He also said the federations of some sports, such as swimming, insist on random testing rather than medal-oriented testing.

Vazquez Rana said today that De Rose was right, but that only one to three percent of the total medalists will not be tested.

"There was a mistake," Vazquez Rana said. "There may have been some instances where this was not done. We are compiling documentation on it."

The issue of the visa denied to a shooter from Chile appears to be one that will not go away.

Today, two representatives from the U.S. State Department appeared before the PASO executive committee to explain why the visa was denied to Daniel Zuniga. Zuniga is accused of being a member of a secret police group that is guilty of human rights violations.

Some executive committee members, including Vazquez Rana, have said the decision is a violation of IOC rules and should jepoardize Anchorage's chances of becoming a site for the Olympic Games.

The state department officials came to convince the committee that they had good reason for denying the visa, Vazquez Rana said. He added that the committee has decided to delay any action until the Games are over.

"We have definitely gathered all the information and left it as a pending decision," Vazquez Rana said. "I can tell you the opinion of PASO and the executive committee is to sanction the U.S. Olympic Committee."

A sanction could come in the form of a condemning statement, he said, declining to elaborate. But the committee could also recommend that no international events be held in the United States.