Thirteen people were found “trapped” under hay bales within a cattle trailer near Alton on Tuesday, federal authorities said in a news release.

Texas Department of Public Safety troopers pulled over a Dodge pickup truck hauling the trailer and a K-9 alerted the authorities to a concealed compartment, the release said.

Thirteen migrants who were illegally in the country were found under bales of hay in an enclosed wooden compartment without ventilation; they were sitting with their knees to their chest and heads bowed, authorities said.

They had been inside the compartment for about an hour when they attempted to cross the Falfurrias checkpoint.

DPS troopers took the driver and two other suspects into custody to be charged with smuggling, the release said.