Thomas Johansson of Sweden, who lost to American Jeff Blatnick in the super heavyweight Greco-Roman wrestling final, tested positive for steriods and must forfeit his Olympic silver medal, a Swedish official said today.

Johansson becomes the third athlete to flunk the sophisticated drug tests in use at the Games, but the first to lose a medal. Steroids earlier had been detected in the urine of one weightlifter from Lebanon and another from Algeria.

"There is no doubt about the reality of what he did," said Wolf Lyberg, chief of the Swedish delegation to the Games. "He has told us himself."

Refik Memisevic of Yugoslavia finished third in the unlimited weight class, so the elimination will give him the silver. Romania's Victor Dolipschi was fourth, so he will move to collect the bronze.

According to Lyberg, Johansson acknowledged that he took one injection of Primobolan, an anabolic steroid, around the first of May. Lyberg quoted Johansson as saying he had lost more than 20 pounds after suffering a broken nose in the European championships and undergoing surgery and needed to put on weight quickly.

Steroids, combined with diet and training, are believed to build up muscle mass.

Lyberg said Johansson was told there would be no trace of the drug in his system after a two-week period. The Los Angeles time quoted Johnasson as saying he bought the steroids during the European championships in late April for $5.

"We are not beating around the bush," said Lyberg. "The young man made a mistake . . .

"He must have done it by stupidity. We had informed all of our athletes who might have been in for something like that."

After Johansson won his silver last week, his father, a grocer, offered free coffee and Danish pastry to the entire village where they live. The village is called Haparanda and there had been joking by Swedish journalists that it would be renamed Happyranda. Now, Johansson will go home Monday.

Mahmoud Tarha of Lebanon and Ahmed Tarbi of Algeria, the weightlifters who tested positive for steroids, were -- after being disqualified from the Games -- banned for life by the International Weightlifting Federation.

Any decision on Johansson's future will come from his federation.