CNN
 — 

If you’re hoping to bring cascarones – confetti-filled eggshells common throughout Mexico – across the border, you’ll have to keep it to 12 or fewer, according to US Customs and Border Protection.

The agency published a news release Thursday reminding travelers they can only bring a maximum of 12 cascarones when entering the US ahead of Easter celebrations.

According to the release, the eggs “may be decorated, etched, or painted but they must be clean, dry, and free of any egg residue.” The egg white and yolk must be removed.

The reason cascarones are restricted is due to the spread of disease, the news release explained. Contaminated eggshells can spread avian diseases like Newcastle disease and Highly Pathogenic Avian Influenza. The warning comes as the US continues to face the deadliest outbreak of avian flu ever seen in the country, with millions of domestic birds catching the disease.

Newcastle disease can kill up to 90% of exposed birds, according to the news release, and Highly Pathogenic Avian Influenza is also linked to “exceptionally high mortality” in birds.

Although cascarones can be brought into the US in limited quantities, fresh eggs, raw chicken, and live birds or poultry are forbidden entirely, according to the news release.