RIO DE JANEIRO (Thomson Reuters Foundation) - Organizers of an international music festival in Sao Paulo were formally accused on Wednesday by a workers’ union of using homeless people to build its stages and subjecting them to slavery-like conditions.

Sao Paulo’s Union for Artists and Technicians in Spectacles and Entertainment lodged an official complaint with the Labor Prosecutor’s Office against Brazilian entertainment company T4F which organized Brazil’s edition of the Lollapalooza festival.

Union President Dorberto Carvalho accused T4F of forcing homeless people to work long hours in dangerous and degrading conditions for little or no pay ahead of last weekend’s festival.

T4F, also known as Time for Fun, which is Brazil’s only publicly-held entertainment company dating back to 1983, would not comment on the accusations. Lollapalooza, a U.S.-based company, did not reply to requests for comment.

“They told me that they were hired to carry heavy structures for 12 hours straight,” Carvalho told the Thomson Reuters Foundation.

“If a person was unable to work the full 12 hours, if they were only able to handle six, they were fired and got nothing.”

The Labor Prosecutor’s Office of Sao Paulo, which investigates and prosecutes labor violations, did not immediately respond to a request for comment.

When a formal complaint is made, the office has to assign a prosecutor to analyze the complaint and see if it merits further investigation.

If a labor prosecutor decides to charge TF4 with engaging in slave labor, the company could face civil and criminal proceedings.

This year, Brazil’s version of Lollapalooza featured artists like the Arctic Monkeys, Sam Smith, Lenny Kravitz and Kendrick Lamar over three days. The cheaper tickets sold for about 800 reals ($207.54).

According to Carvalho, about 120 homeless people worked on the event, found through a contractor hired by T4F. They were paid about 45 reals ($11.67) per day, had no safety gear and were not given contracts.

Those who did maintenance during the event were kept in a locked room so they wouldn’t mingle with the paying public, said Carvalho, who spoke to some of the homeless workers.

In Brazil, slavery is not defined as just forced labor. The term also covers debt bondage, degrading work conditions, long hours that pose a health risk and work violating human dignity.

The alleged labor violations were initially reported on Saturday by Folha de Sao Paulo, a Brazilian newspaper, that spoke to several homeless people and also to the Rev Julio Lancelotti, a Catholic priest who works closely with the homeless.

Lancelotti said he first noticed the problem during last year’s Lollapalooza when homeless people asked him if they could borrow shoes.

Prospective employers go door-to-door to homeless shelters in Sao Paulo in search of cheap labor to do the heavy work of building stages for events, Lancelotti said.

“They pick the ones that have shoes, so that’s why they were asking me for them. Most only own flip flops,” he said.

“They carry heavy structures, and sometimes they get hurt ... It is analogous to slavery. It is highly exploitative.”

Brazil officially recognized the active use of slave labor in 1995 and launched a special mobile enforcement group to work with prosecutors and police to find and raid farms, construction sites and companies suspected of using slave workers.

Since then, about 50,000 people have been freed from slave-like work, according to government figures, most of them men who are either illiterate or have not completed basic education.