BOGOTA (Thomson Reuters Foundation) - Colombian authorities arrested a dozen people on charges of trafficking girls into prostitution as part of an international human trafficking ring that preyed on poor teenagers in a jungle town in the country’s south, state prosecutors said on Monday.

Eight girls were rescued in the weekend operation that followed a joint investigation by police from Colombia, Peru and Brazil, which share borders that meet at the Colombian town of Leticia along the Amazon River.

The girls, aged 14 to 16, were lured at a park in Leticia with false promises of good jobs but made to work as prostitutes in bars in neighboring Brazil and Peru, according to Alvaro Osorio, a senior Colombian state prosecutor.

“They took advantage of their vulnerability,” Osorio said. “The girls come from poor families.”

As many as 50,000 Colombian women are trafficked into prostitution abroad each year, according to U.S. government figures, but the number of trafficking convictions is low.

The number of convictions for trafficking in Colombia was 31 last year, up from seven in 2014, according to the U.S. State Department.

Worldwide, the human trafficking industry is worth some $150 billion a year, according to the International Labour Organization.

In Colombia, the most vulnerable women and girls are indigenous and Afro-Colombian.

Some of the girls lured from Leticia would disappear for a week or as long as three months, their parents told authorities.

Some became pregnant, and some were forced to have abortions by the traffickers, Colombian police said.

If convicted, the traffickers could face up to 23 years in prison.