GANADO, Texas (AP) — Deputies found about 100 migrants in the back of a semitrailer that had broken down on a South Texas highway on Friday, but many of them fled, authorities said.

Deputies with the Jackson County Sheriff’s Office found the semitrailer around 7 a.m. just north of Ganado, about 90 miles (145 km) southwest of Houston.

When authorities opened the back of the vehicle, many of the occupants — whom authorities suspect illegally immigrated into the U.S. — jumped out and ran away into nearby brush and corn fields, the sheriff’s office said.

Deputies took 64 people, including the semitrailer’s driver, into custody. The individuals who are illegally in the country are being processed by the U.S. Border Patrol, said Jackson County Sheriff Kelly Janica. Authorities were still searching the area for about 40 other migrants who fled on foot.

Nine of the people detained were treated at Jackson County Hospital for dehydration, Janica said.

Authorities did not say how long the migrants were inside the tractor-trailer before they were discovered.

Various other agencies, including the Corpus Christi Fire Department and the Texas Department of Public Safety, helped the sheriff’s office search for and treat the migrants who were taken into custody.