The nine plastic jars contained about 300 leeches in total and came in six air cargo shipments from Bulgaria between February 19 and February 25, according to a release issued by the U.S. Customs and Border Protection. They were meant to be shipped to addresses in Connecticut, Florida and Illinois.

The leeches were identified by labels on the jar as Hirudo orientalis, but after officials turned them over to a U.S. Fish and Wildlife (USFWS) inspector, they were identified as Hirudo medicinalis, which are endangered leeches used for medicinal purposes.

Per the University of Michigan Museum of Zoology, Hirudo medicinalis is found through western and southern Europe to the Ural mountains in Russia and countries bordering the northeastern Mediterranean.

These leeches are parasitic and adults feed on the blood of mammals.

“It attaches to the host by means of its two suckers and bites through the skin of its victim,” officials with the zoo said.

The feeding process lasts between 20 and 40 minutes, and when the leech is finished feeding, it leaves a star-shaped scar behind.

They’ve been used to remove the “bad blood” of those who were sick in the past, but they have a new use.

“Today this species is used to relieve pressure and restore circulation in tissue grafts where blood accumulation is likely such as severed fingers and ears,” the piece said.

However, because they have been overharvested, these leeches are rare in Europe.

“The USFWS inspector determined that the shipments violated the U.S. Endangered Species Act, which prohibits the unlicensed possession, trade, import and export of protected species of wildlife or wildlife products,” the release stated.

Stephen Sapp, the public affairs officer for the U.S. Customs and Border Protection, told Newsweek there are permits someone can fill out to import leeches, but approval is contingent on meeting certain requirements under the Endangered Species Act.

Because many purchases are made online, he said someone may have made an order without getting a permit.

Border authorities frequently find questionable items that come into the country.

At the end of January, for example, officers found a taxidermied bird in a display case addressed to Quebec, Canada, from Hull, United Kingdom, per the release.

Beyond receiving shipments of wildlife, Sapp said officials have also seized deliveries of pharmaceuticals, like steroids, oxycodone and liquid ecstasy.

Newsweek reached out to the U.S. Fish and Wildlife Service for comment.