Customs officers discovered an unorthodox souvenir in a traveler’s suitcase in Detroit last week.

The officers found six giant African snails in a passenger’s luggage, and the snails were still alive, according to a news release from U.S. Customs and Border Protection.

“Our CBP officers and agriculture specialists work diligently to target, detect, and intercept potential threats before they have a chance to do harm to U.S. interests,” said Port Director Robert Larkin in the release. “The discovery of this highly invasive pest truly benefits the health and well-being of the American people.” 

The snails are considered a delicacy in West Africa and are served as finger foods in some areas. Some people also like to keep the snails as pets, per NPR.

Why are giant African snails illegal in the U.S.?

The African snails “can carry a parasitic nematode that can lead to meningitis in humans,” and can also wreak havoc on structures and ecosystems in areas where the snails aren’t native, according to the release.

The parasite is called rat lungworm, and some will eat the plaster off of houses, CNN reported.

What happened with the giant African snails in Florida?

Florida had to place Pasco County under a quarantine order after giant African land snails were discovered in July because the snails breed rapidly, laying up to 2,500 eggs per year. Experts believe the snails arrived through illegal pet trade, per CNN.

When giant African snails were discovered in southern Florida in the 1960s, it required $1 million and 10 years to get rid of the invasive species, NPR reported.