Acapulco, Mexico: On any sultry Acapulco night, Mexican boys move among the partying crowds on the oceanside boulevard, doing whatever they can to make a...living.

For a dollar or so, the street boys will dive from a high rock into roaring surf. At busy street corners they become human flame throwers, spitting mouthfuls of lighted kerosene into arcs of fire, then passing the cup to motorists before the traffic signal turns green.

Some of the boys who roam the streets who used to earn a meal and a place to sleep by following American men to their Acapulco hideaways and having sex with them or with one another in front of a video camera, investigators say.

With a series of arrests that began in May, the U.S. Postal Service closed down what it said was the biggest child pornography production and distribution ring the U.S. law enforcement officials had ever seen. The $500,000-a-year business was run by...Americans, they said, and was based in a high-priced hillside home overlooking Acapulco's famous bay.

In the thousands of videos and photographs seized by Mexican and U.S. police, investigators counted about 300 boys who appeared to be underage Mexicans. Many were recruited on beaches, in public parks and on the doorsteps of bars in Acapulco, they say. The youngest children looked to be no more than 7 years old.

So far, 56 persons across the United States have been arrested and charged with receiving - by mail order - videotapes showing sex involving underage boys. Officials expect the number of arrests to exceed 100.

Postal investigators say the ringleader was Clair Anthony (Troy) Frank, a fugitive from American justice with a criminal record for molesting minors and selling child pornography... They said he made hundreds of videos in and around Acapulco, including many at poolside on his own front patio. In some of the films, sex with minors was accompanied by violent beatings.

The sexual abuse of minors has long been tolerated in Acapulco, a tropical beauty in decline that has become a prime destination in the global boom in sex tourism.

"There is a...increase in international travel, and some people travel with the attitude...nobody's going to know me if I go there," said John Rabun, who monitors sexual crimes involving children for the National Center for Missing and Exploited Children in Arlington, Virginia.

U.S. officials say Mr. Frank's film business is finished. On Aug. 2, 1995, he was found dead...in his residence here with a gunshot wound to the head... One man wanted in the United States and Mexico as a partner, John William Willets of Sunnyvale, CAlifornia, is a fugitive. Another, James Leroy Kemmish, was arrested in San Diego in 1994, pleaded guilty to charges of distributing child pornography through the mail, and is serving a five-year sentence.

...many young people who inhabit Acapulco's central square...still talk about the "gringos" - the Americans who offered to pay them to perform on camera.

One boy who dwells on and off in tne square is a spindly 11-year-old known on the street as Juanito G. After leaving home to escape the blow of his mother's boyfriend, he said, Juanito lived for months in the square and recently sought refuge in a public shelter for boys. He recalled the evening when an American came to the square to invite more than a dozen boys to his home - "a rich man's house," Juanito said - to see some movies.

"He showed us the film, and then he asked us to help him make one," Juanito said.

Like several boys who spoke about the films, Juanito said he had not taken part himself but had a friend who did. The rates started at 100 pesos, or about $15. ...

Counselors at the shelter say they found out about Juanito's knowledge of pornography one day when they put a cartoon on the video players for the boys to watch. Juanito...demanded to see a movie with explicit sex.

...as he talked about his experience, his smile disappeared. ...

"I never said a word to that gringo," he said... "I only watched. I'm only doing that with the girl I marry."

Another boy who said he was solicited to make a pornography film is a 9-year-old who lived for a time in...the main square.

Some minors were paid if drugs to make films, he said, while others were not paid at all in order to pressure them to return for another session.

Many Acapulco street children are drug users, prowling for pesos to buy paint thinner, glue or marijuana.

The boy expressed contempt for a friend who...consented to be in a pornography film.

For the Mexican boys who were caught up in Mr. Frank's operation, there is little help or protection. The public social welfare system, already collapsing under a severe economic crisis, has no methods for eaching out to children in this kind of case.

At the same time, Mr. Frank left behind a veil of shame. Although several hundred boys were believed to be involved, neither the social agencies nor the police in Acapulco received a single complaint from any of the boys or their families.

Leticia Castro Ortiz, Acapulco's chief detective for child abuse cases, said, "There is nothing out there but silence."