The U.S. Border Patrol and the Texas Department of Public Safety helicopter crew seized $430,000 worth of marijuana.
Agents said they discovered more than 530 pounds of marijuana while patrolling near Anzalduas Park in Mission.
A truck entered the park with its headlights off. Agents called for DPS air support.
Troopers reported seeing about 20 people cross the Rio Grande into Mexico using an inflatable raft and an aluminum John boat.
DPS also reported seeing the subjects on the south side of the river with bundles of what appeared to be narcotics.
Before fleeing to Mexico the smugglers abandoned the truck and 39 bundles of marijuana.
The abandoned vehicle, a Ford F-250, was later discovered to have been reported stolen out of McAllen. Border Patrol agents transported the marijuana and the stolen pickup to the McAllen Station for processing.