In March, Louisville CBP seized three shipments of "hatching eggs." In total, 39 eggs were stopped from entering the U.S. "Hatching eggs are all avian species to include poultry, game birds, racing pigeons, and other birds -- if there is a market for a live bird, someone will try to import hatching eggs for them," officials said.

Why are customs agents concerned about eggs being brought into the country? Here's a look at the issue and why it's dangerous.

Shipments of ready-to-hatch eggs have been seized three times this month at a port of entry in the Midwest, as agriculture officials work to slow the spread of avian influenza, or "bird flu."