Getting access to a "maquiladora", one of the hundreds of factories that line Mexico's border with the United States, was the biggest challenge of shooting Lorenzo Vigas' latest film at Venice, the director said Monday. 

"The Box" is in competition for the top prize at the Venice Film Festival, to be announced on Saturday.

It was shot in Chihuahua, the site of hundreds of foreign-owned factories assembling cheap goods and apparel for the United States just across the border, and one of Mexico's most violence-plagued states.

The cheap labour that fuels the maquiladoras has made Mexico a major exporter, but at the cost of its poor and uneducated workers, many of whom work in sweatshop conditions for rock-bottom wages.

"How do you put a camera inside a real maquiladora? It's nearly impossible," the Venezuelan director, who lives in Mexico, told journalists Monday.

"They're very jealous of not exposing their production line," said Vigas, who in 2015 became the first Latin American to win Venice's prestigious Golden Lion with his first feature, "From Afar".

"They're very jealous of not exposing the condition of their workers -- so how do you shoot a film?"

The production team spent nearly a year trying to find a maquiladora that would allow the crew to shoot inside, before finally getting the green light from a company that was ready to close for bankruptcy.

"We didn't get any roadmap from people who had done this before -- because nobody was allowed before to do this," said one of the film's producers, Jorge Hernandez Aldana.

Missing women 

The film tells the story of a 13-year-old boy (first-time actor Hatzín Navarrete), who travels halfway across Mexico to recover the remains of his father, whose body has been found in a mass grave.

On the way, he hooks up with a man, played by Hernan Mendoza, who supplies workers for the maquiladoras. He signs up poor people in remote villages with a pitch that they must protect Mexican jobs from Chinese competition.

When we finally see inside the jeans assembly factory where the workers are taken, in the middle of a bleak, unforgiving desert, we immediately wish they could turn back -- it's loud, hot, and the pace is non-stop.

Besides its central theme of replacing absent fathers, "The Box" touches on the brutal reality of thousands of women there -- many of them maquiladora workers. Since the 1990s hundreds have been abducted, either vanishing entirely or their bodies turning up discarded or buried in the desert.

"More than 20,000 women in the north of Mexico have disappeared," said Vigas. "Nobody knows why."

More than 73,000 people in Mexico are missing, the government said in 2020, a quarter of them female. 

Another Latin American film in competition is "Sundown" from Mexico's Michel Franco. His "New Order" with its searing indictment of the gap between rich and poor in Mexico, won Venice's Silver Lion last year.

"Sundown" stars Tim Roth as a man escaping his obligations at a time of family crisis to hang out on an Acapulco beach.

But, just as in Vigas's film, an undercurrent of social tension pervades the quiet drama, keeping the viewer on edge -- and even a tranquil beach holiday in Mexico is not enough to keep violence at bay.