BROWNSVILLE, Texas — Customs officers have found 5,000 rounds of ammunition commonly used in assault rifles in a SUV crossing back into Mexico.

Customs and Border Protection announced Friday that a Mexican citizen was caught in a southbound inspection at the Gateway International Bridge in Brownsville on Wednesday. Boxes of ammunition were found under the back seat of the Ford Excursion.

The driver, a 21-year-old man from Matamoros, Mexico, was turned over to Immigration and Customs Enforcement.

Authorities occasionally inspect southbound traffic at the international bridges looking for cash and weapons.