Steroids found in athletes at this year's Pan American Games may leave traces still detectable at next year's Olympics, using ultrasophisticated testing that officials say finally detonated "a time bomb" over amateur sports.

And the medical director of the Los Angeles Olympic Organizing Committee said the Pan Am scandal should serve notice to all that illegal drug use during the 1984 Olympics will not be tolerated. "We will have equal or better testing for the Olympics," said the director, Dr. Tony Daly.

The disqualification of four medal winners in weightlifting today, bringing the two-day total to 11 who tested positive for steroids, of whom eight were stripped of medals, bore out that testing here has been the most intensive and extensive ever.

Twelve members of the U.S. track and field team left today, deciding not to compete after being told of the testing.

One of them, triple jumper Mike Marlow of Los Angeles, interviewed at the Caracas airport by ABC Radio, said the tests may be too revealing.

"We knew that a strict test could find anything--caffeine, alcohol, anything," he said.

Nevertheless, the U.S. Olympic Committee strongly endorsed the tests, and its executive director, F. Don Miller, said the facilities at the 1984 Olympics will be "every bit as good as the equipment here."

Dr. Roy Bergman, head physician for the U.S. Pan Am team, said all drugs leave "footprints" in the body, and the testing laboratory in Caracas can detect banned substances for a year or even longer. With the Olympics less than a year away, it may be too late for some athletes to compete safely in Los Angeles.

"We have known for some time it was a problem which truly existed, a time bomb ready to explode," said William Simon, president of the USOC. "I frankly welcome this. The justice has been swift and severe and the international governing bodies will decide the sanctions."

He said the USOC will present a proposal "to take whatever steps possible to see it does not occur in the Los Angeles Games."

Simon also said the United States will consider pretesting its athletes before future international events, something it has resisted in the past.

Six athletes were disqualified following positive drug tests at the 1976 Montreal Olympics, and seven East European women were banned from international competition in 1979 for taking drugs. In 1978, four Soviet athletes and a Bulgarian were disqualified from the European Track and Field Championships on doping charges.

But the testing had been sporadic, at random at some events and not at all at others.

Improper steroid use, said Simon, "has to stop and this might stop it."