efe-epaTucson, Arizona

Scientists performing an experiment in the Arizona desert with bodies of dead pigs fear that the official number of undocumented immigrants who died after crossing the border from Mexico is nowhere near the real number.

"We're sure that many more people died in the desert and that we just never found their bodies," Jason de Leon, anthropologist and director of the Undocumented Migration Project (UMP), based at the University of Michigan, told EFE.

De Leon directs a team that since 2012 has carried out three experiments at the height of summer in the Arizona desert in order to find out what happens to immigrants who die crossing that dangerous arid land.

Pig bodies are used in the experiments because of their similarity to humans.

According to official US Border Patrol figures, between 1998 and 2017 the deaths of 7,216 undocumented immigrants have been reported along the border with Mexico, including 2,726 within the Tucson Sector.

The experiments with pigs, the most recent completed in early July, "show that the environment and scavengers can quickly destroy a body, in less than three or four days, which is why I believe we're never going to know the complete number of dead (immigrants) in the desert," De Leon said.

The researchers document step by step what happened to the bodies by means of video cameras and images caught by aerial drones.

Tougher immigration policies along the border over the past 20 years, plus greater surveillance and the use of technology, has forced immigrants to cross the border at very remote, dangerous areas, including the Arizona desert.

"The desert cleans up all the government's dirty work - there's no evidence. The bodies simply disappear, which is why we're doing these experiments to show the public what's happening," De Leon said.

In its most recent research, the team was surprised at how the body of one of the four pigs placed near the town of Arivaca disappeared in six days.

In less than two weeks, all the pigs had been devoured by scavengers, torn apart and their bones scattered across the desert.