Federal police rescued 38 undocumented immigrants who were being smuggled to the United States in a tractor-trailer under "conditions that put their lives in danger," Mexico's Public Safety Department said.

The group comprised 22 Hondurans, six people from El Salvador, four Guatemalans and six migrants from the Asian nation of Nepal, the department said in a statement.

Police found the migrants in an industrial district of the capital as part of an investigation into an international trafficking ring.

The alleged leader of the ring, Josue Israel Medel Loaiza, and two other people were arrested while loading the migrants onto the trailer, which had Illinois license plates.

The migrants had already made two payments to the traffickers and the final sum would be due once they were safely on U.S. soil, the Public Safety Department said.

Police seized a pickup truck, the tractor-trailer, three two-way radios and three cell phones.

Several hundred thousand migrants cross Mexico every year trying to reach the United States. EFE