McALLEN, Texas (Border Report) — A barrel of spider monkeys has been confiscated by federal officials at a port of entry in Progreso, Texas, where they said someone was trying to illegally smuggle the endangered species across the border.

The four spider monkeys were not declared by the female 20-year-old driver as she approached the Progreso International Bridge on Dec. 30, U.S. Customs and Border Protection officials said Tuesday.

The woman, a U.S. citizen, was sent to secondary inspection where the four monkeys were discovered “concealed inside a duffle bag,” in the Jeep, CBP said in a news release.

“While conducting their inspections, our officers will often encounter a myriad of prohibited agriculture products,” Progreso Port Director Walter Weaver said. “Sometimes these encounters yield hidden exotic animals, such as in this case.”

Spider monkeys are endangered under the Endangered Species Act and are typically found in tropical forests of Central and South America.

The driver was issued a penalty and CBP officials said they returned the monkeys to Mexico.

Sandra Sanchez can be reached at ssanchez@borderreport.com.