LOS ANGELES - Pornography film shoots across the United States have been largely shut down after an industry trade group called for a moratorium because an adult-film performer tested positive for HIV, officials with the organization said on Tuesday.

The temporary moratorium recommended by the Los Angeles-based Free Speech Coalition comes as public health advocates escalated calls for greater enforcement of laws requiring porn stars to wear condoms on the set.

The Free Speech Coalition said it learned on Saturday that a porn film performer who has not been publicly identified had initially tested positive for HIV. It called for an industrywide moratorium on Sunday.

The performer received a preliminary positive result for HIV, the virus that causes AIDS, at a health facility outside of California. The San Fernando Valley suburb of Los Angeles has long been a leading hub of the porn industry.

Further diagnostic testing was needed to confirm the performer was HIV positive, the trade group said.

Diane Duke, executive director of the trade group, said she believed porn productions had largely been shut down nationally as a result of the moratorium, and that she was unaware of any companies that were refusing to comply.

"The industry has had a successful system of health and safety self-regulation since 1998, despite any misinformation being spread by our opponents," the Free Speech Coalition said in a statement.

In 2010, another porn performer, Derrick Burts, tested positive for HIV, which also prompted a temporary shutdown of porn productions.

A number of other porn stars have been infected with HIV over the years, said Brian Chase, assistant general counsel for the AIDS Healthcare Foundation, which was organizing a petition drive for a Los Angeles municipal ballot initiative to require porn performers in the city to wear condoms on set.

Supporters said local authorities were best suited to enforce such a measure.

California law and federal workplace safety rules require the use of condoms for porn stars exchanging bodily fluids through sex, but the industry has largely ignored those mandates, Chase said.

Porn companies have resisted efforts to compel condom usage by arguing it would force productions to go underground or outside the United States, increasing health risks.

The porn industry continues to operate in a legal gray zone, Chase said. "When you've got a situation like that, you've got a lot of industry participants who feel they don't need to follow the law," he said.