The shipment of three separate containers was discovered last Wednesday at the facility after employees saw the package was "not labeled properly," Southwest spokeswoman Ashley Rogers said. "Although it is common to transport human specimens for medical purposes, a longstanding Southwest cargo customer attempted to transport a shipment without following policies in relation to labeling, packaging, and properly declaring the contents," the company said in a statement on its website.

Southwest employees opened the box last Wednesday evening, found the heads and contacted local police, who turned the heads over to the local coroner. "They were basically in plastic containers with lids that are not air-sealed," Coroner Garland Camper said. "They were duct-taped with minimal information to disclose what was inside."