MEXICO CITY - Mexican public health officials are sounding an alarm after a study discovered the presence of animal tranquilizer Xylazine in opioids in cities on the country's northwest border with the United States.

Known popularly in English by names like "tranq dope" and "zombie drug," Xylazine cut into heroin and fentanyl has in recent years worsened the opioid scourge in U.S. cities like Philadelphia.

On April 8, Mexico's health ministry in conjunction with the mental health and addiction commission (CONASAMA), issued an alert "for health personnel and first responders in Mexican border cities for possible adulteration of heroin and fentanyl with Xylazine."

Because it is a sedative but not an opioid, Xylazine can make opioid overdose reversal treatments less effective and raise the risk of fatal drug poisoning, while also causing severe skin abscesses that can be life-threatening.

In Mexico, like in the United States, Xylazine is only approved for use in animals, not humans.

The government's alert pointed to a study that tested 300 samples of drug residues in the cities of Tijuana and Mexicali, identifying Xylazine as an adulterant in 35 residues of heroin mixed with fentanyl and 26 fentanyl residues.

The study, which is ongoing and has not yet been published, is funded by Mexico's National Council for Science and Technology (CONACYT).

The study was seeking to identify adulterants in drugs and was not specifically looking for Xylazine.

"We were surprised to find Xylazine," said Clara Fleiz, an investigator at Mexico's National Institute of Psychiatry and the study's lead author.

The alarm comes amid signs the consumption of fentanyl, the highly potent synthetic opioid fueling tens of thousands of deadly overdoses per year in the United States, is spreading within Mexico's borders.

  - Reuters