INDIANAPOLIS -- Unnerving explosions could be heard -- and felt -- during the Pan American Games' gold-medal showdown between the United States and Canada in men's softball Thursday night.

Fans had become accustomed to the pop-pop of balls whistling into the catcher's glove in a strikeout-dominated sport; these were bleacher-rattling bangs.

"Not to worry," the field's public-address announcer eventually said. "It's just {fireworks} practice for the closing ceremony."

The Pan Am show that ends Sunday has been the uneven mixture of tense politics and compelling sport -- and sportsmanship -- that figures to come from half the hemisphere at play.

Unless something ugly develops in the final hours, this Pan Am scorecard has athletics kicking the bejabbers out of politics. For a pleasant change. Or perhaps international games and those who watch them are maturing.

"Drugs Return to Haunt Games," read the headline in a Chicago paper earlier this week. Six athletes testing positive for drugs cracked front pages nationwide.

Folks, that's six positives out of 400 results. Assuming the testing procedures were adequate, one alleged cheater for every 67 performers is not bad at all for humans under exceptional pressure.

More scary was the later revelation of a few positives for a drug-masking agent not on the list of about 3,700 banned substances. Reportedly, two U.S. gold-medal winners were involved. So the science of athletic cheating may also be advancing.

Evidence so far insists these Games are three times cleaner than the '83 Games, when 19 athletes tested positive.

My major surprise here was that not all medal winners were tested. I had thought that was fundamental policy for all games of this magnitude; it is not.

Each sport's governing body determines which athletes, and how many, will be tested. The shooting federation, reports said, refused to let all its medalists be tested; the fencing federation, meanwhile, wanted more tests than the medical commission did.

Diplomatic immunity of a sort also extends to the international playpen. That apparently is why those Cuban boxers and security agents who fought with anti-Castro demonstrators during the boxing competition last week will not be prosecuted.

Besides, who provoked who might be difficult to determine. I was witness to a shouting fuss between a Cuban-American, living in Los Angeles, and three Cuban journalists at boxing a few days later -- and the blame seemed equal.

There were threats earlier this week that the Cubans would boycott the closing ceremonies, for a variety of reasons; yesterday, there was an official announcement that the Cubans will attend and reports that a high-ranking official in the Cuban government may also come.

Passions clearly are too hot for the former Washington Senators farmhand, Fidel Castro, to jet in.

Some tension during the games gave neutral witnesses much entertainment. The most bizarre was a Mexican trainer suddenly running onto the soccer field and tripping a Brazilian player on a breakaway.

The American football analogy would be the Redskins' Bubba Tyer scurrying from the bench at RFK Stadium and blindsiding Tony Dorsett. The Mexican intruder helped contribute to the match being suspended 56 seconds from the finish, and to Brazil, which led, 1-0, at the time, being declared the winner.

Fairly extensive venue-hopping over most of two weeks has produced these opinions: the most overrated Pan Am sport is water polo; the most underrated Pan Am sport is team handball. The most overlooked Pan Am country is Canada; the Pan Am competitor who tugs hardest at your heart is Liz Mizera.

The most intriguing message was the one stitched near the bottom of a Suriname banner: "A dirt wagon carries dirt, but it does not carry shame."

For the near-ultimate in athletic boredom, try water polo. It's a couple of dozen guys beating water -- and each other -- in a bathtub the size of a basketball court, with two officials whistling everything to a halt every few seconds.

Lots of others agree. A survey in a local paper showed that slightly more than a third of the spectators at water polo got in for nothing. No other sport had close to such a percentage of freebees. Fortunately, the silly splashing only lasts 28 minutes.

Team handball has been called water polo without the water. Nevertheless, I'm fond of it. At least you don't have to search for welts after the matches to realize only the hardy take part.

Most attention during these Games has been focused on the Americans and the Cubans. The United States has more than twice as many medals as anyone else; but the country with the second highest total is Canada.

Of the 6,000-plus athletes, none was more endearing than the one who could be found at shortstop for the U.S. women's softball team. Mizera grips life as firmly as her bat.

"I go six months to six months," she smiles.

That is the amount of time between checkups for the cancer everyone hopes has been rooted out of her left hand for good. A complicated operation about three years ago left her with a mangled-looking and useless thumb.

So splendid was she this spring and summer that the best non-pitcher in women's softball, Dot Richardson, was moved from shortstop to second base to make room for Mizera. Her single scored the final U.S. run in its 4-1 victory over Puerto Rico for the gold medal.

At age 20, Mizera has accomplished a rare triple this year: playing on the team what won the Amateur Softball Association championship, playing on the team that won the NCAA championship and playing on the team that won the Pan Am championship.

"Softball is a medal sport in the Olympics in 1992," she said. "My goal is to be on our team."