The United States announced Tuesday a crackdown on unlawful imports of xylazine, an animal tranquilizer known as the "zombie drug" and which is increasingly linked to overdose deaths.

Xylazine, which also goes by the street name "tranq," has recently been found in illicitly manufactured fentanyl, heroin, cocaine and other drugs, presenting a "growing public health concern," the Food and Drug Administration (FDA) said.

"This action aims to prevent the drug from entering the US market for illicit purposes, while maintaining availability for its legitimate uses in animals," it said in a statement.

According to the National Institute on Drug Abuse, the percentage of all drug overdose deaths involving xylazine increased from two percent to 26 percent in the northeast state of Pennsylvania from 2015 to 2020.

Xylazine is typically used by veterinarians to sedate large animals such as horses and deer but the drug is not approved for use in humans.

It can slow breathing, blood pressure and heart rate to critically low levels and cause skin ulcers and abscesses that can lead to amputation.

The FDA said imports of xylazine would be subject to heightened scrutiny and seized if they appear to be unlawful.

"The FDA remains concerned about the increasing prevalence of xylazine mixed with illicit drugs, and this action is one part of broader efforts the agency is undertaking to address this issue," FDA commissioner Robert Califf said.

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