MEXICO CITY – Mexican police detained 60 undocumented migrants in the northwestern state of Sinaloa, most of whom had been crammed into two hidden compartments of a cargo truck.

Federal Police officers intercepted 58 Guatemalans and two Salvadorans, including four minors, who were riding in the vehicle on the Mexico City-Nogales highway near the town of Escuinapa, the Public Safety Secretariat said in a statement Friday.

A total of 59 illegal migrants “were traveling in life-endangering conditions” in the back of the truck. Another undocumented Guatemalan man was riding alongside the driver, 18-year-old Isaac Contreras Sanchez, who was arrested.

“The action was the result of security patrols and monitoring by Federal Police,” who searched the truck and became suspicious when the driver could not show proof of authorization to transport furniture and mattresses.

The officers then inspected the vehicle and found people stashed inside two compartments beneath some of the mattresses, the statement said, adding that they were calling for help “due to the conditions in which they were traveling.”

The truck had departed from the central city of Puebla and was heading for the small town of Pitiquito, located in the border state of Sonora.

The officers “at all times respected the rights and physical safety of the migrants, who were provided with food and medical care,” the statement said.

Large numbers of Central Americans undertake the hazardous journey across Mexico each year on their way to the United States, although the number of border crossers fell from an estimated 433,000 in 2005 to 140,000 in 2010, according to official figures, due to recent U.S. economic woes and heightened security.

The trek is a dangerous one, with criminals and corrupt Mexican officials preying on the migrants.

Gangs kidnap, exploit and murder migrants, who are often targeted in extortion schemes, Mexican officials say.

Central American migrants follow a long route that first takes them into Chiapas state, which is on the border with Guatemala, walking part of the way or riding aboard freight trains, buses and cargo trucks.