U.S. Border Patrol agents made a surprising discovery last weekend when they arrested a migrant carrying a backpack filled with seven spider monkeys, federal authorities said.

Agents found the monkeys on Sunday when a Mexican juvenile was apprehended in Brownsville, Texas, which is on the U.S.-Mexico border, officials said in a statement. The Border Patrol’s Rio Grande Valley Sector posted a video on Facebook showing the monkeys huddled inside a bag that appeared to have holes in it to allow the animals to breathe.

“Extremely proud of our agents for stopping this wildlife smuggling attempt of these critically endangered animals!” the Facebook post reads.

The migrant was arrested and the monkeys, which make their home in Central and South America, were turned over to the U.S. Fish and Wildlife Service. Officials did not release any information about the condition of the animals.

Spider monkeys are considered critically endangered and are among the 25 most threatened primates in the world, according to the Wildlife Conservation Society.

“This case highlights the lengths smugglers will go to maximize profits with no regard for the lives of migrants or animals,” said Rio Grande Valley Sector Chief Patrol Agent Gloria Chavez.

Attempts to sneak exotic animals into the U.S. are relatively common. Earlier this year, 29 Amazon parrot eggs were seized from a smuggler at Miami International Airport. The Rare Species Conservatory Foundation was able to hatch 26 of the 29 eggs, and 24 of the 26 chicks survived.

Last November, federal prosecutors charged eight people with smuggling endangered long-tailed macaques into the U.S.

Last August, a man in California pleaded guilty to smuggling more than 1,700 wild animals into the United States from Mexico.