A Mexican man attempted to cross a Customs and Border Protection checkpoint north of Laredo, Texas, in May, but when suspicious law enforcement officers cracked the seal of his trailer, they found 85 people locked inside.

Jose Luis Vega-Arzate, 31, told officers he volunteered to drive the trailer in exchange for a large reduction to his own $8,000 smuggling fee, according to the U.S. attorney for the Southern District of Texas.

He pleaded guilty to conspiracy to transport noncitizens for financial gain last week and faces up to 20 years in prison when he is sentenced in October.

U.S. Border Patrol agents check a car's occupants and use a dog at a checkpoint coming into the U.S. outside Laredo, Texas. (Reuters/Rick Wilking)

Vega-Arzate pulled into the border patrol checkpoint on May 11 and "displayed nervous behavior and had trouble shifting gears," authorities said.

REP. BIGGS WARNS OF MORE MIGRANT DEATHS AT BORDER IN SUMMER MONTHS: 'IT'S OVERRUN RIGHT NOW'

A K-9 then alerted to the trailer, indicating that it may have people inside.

"At that time, Vega-Arzate told authorities that he had agreed to pay $8,000 to have himself smuggled from Mexico into the country and transported to Austin," the U.S. attorney said. "He did not possess experience or a commercial driving license to drive a tractor trailer in Texas."

Vega-Arzate was told to avoid stopping the trailer on the way through Texas because of the poor ventilation, according to the U.S. attorney.

CLICK HERE TO GET THE FOX NEWS APP

Vega-Arzate's arrest came about six weeks before 53 migrants were found dead in a tractor trailer in San Antonio.

Authorities arrested four men in connection with that case, which was the deadliest human smuggling incident in U.S. history.

Mexican national pleads guilty to trafficking dozens of migrants to pay his own smuggling fee

The man got a reduction in his own smuggling fee to drive the trailer from Mexico to Austin, Texas, prosecutors said