Agents found two AK-47s, loaded and left by the river. Each assault rifle had one round of ammunition loaded in the chamber and 29 additional rounds in the magazine.
Agents were responding to a call about a suspicious vehicle when they found the weapons. The assault rifles and ammunition were turned over to Immigration and Customs Enforcement.
There was no word on whether smugglers left the rifles in the grass near the river.
Border Patrol agents credit an alert citizen for tipping them off to suspicious activity in the area.