According to KDVR, the heads belonged to Science Care, a program for people who want to donate their bodies to science. However, according to a statement from the company, the heads — or the “donated tissues” as they put it — were in the possession of a third-party company that handles shipping, and the box containing them was stolen from their truck.

The company described itself as “the first accredited non-transplant tissue bank in the world. They gave their account of what happened. “Recently, an incident occurred in the Denver area where a sealed box containing donated tissues was stolen from a secured truck operated by a third-party specializing in the logistics of donated tissues,” the statement read. “The secured truck was in the process of returning the tissue to Science Care after a medical training event. Unknown individuals illegally broke into the truck and robbed it of the Science Care box.”

According to the statement, Science Care has been working closely with investigators. “We are doing everything we can to locate the stolen tissue and protect the community. Due to the sensitive nature of our business, and as there are several ongoing investigations, we do not have any further comment on this criminal matter.

According to CBS News, police had warned of “vehicle-related crimes such as auto theft and theft from motor vehicle continue to be a problem in Denver,” only days before the box of heads was stolen.