The two are now in custody of immigration authorities.
Six other people injured in the crash remain hospitalized.
Eleven people were pronounced dead at the scene Sunday night after a 2000 Ford F-250 carrying 23 people veered off U.S. Highway 59 between Berclair and Goliad and struck two trees.
Four other people died in hospitals, raising the death toll to 15.
The passengers were illegal immigrants from Honduras and Guatemala. The driver of the vehicle, who died after being transported to a hospital, was a Mexican national.