Law enforcement agencies across the country are raising alarms about the increasing trend of finding heroin laced with an extremely lethal elephant tranquilizer called carfentanil, The Washington Post reports.

The drug is 10,000 times stronger than morphine and 100 times stronger than fentanyl, just two milligrams of which is lethal—that’s about one toss of a salt shaker. Carfentanil can be absorbed through the skin, and just a puff from re-sealing a plastic bag can be lethal, raising risks for first-responders. Just a whiff can kill a drug-sniffing dog.

Though authorities are struggling to identify it in overdose cases—and sometimes not trying due to the health risks—carfentanil has been linked to dramatic increases in overdoses, which were already at alarming levels amid the nationwide opioid epidemic.

“Carfentanil is surfacing in more and more communities,” DEA Acting Administrator Chuck Rosenberg said in an initial alert last fall following reports from Ohio and Florida. “We see it on the streets, often disguised as heroin. It is crazy dangerous. Synthetics such as fentanyl and carfentanil can kill you. I hope our first responders—and the public—will read and heed our health and safety warning. These men and women have remarkably difficult jobs and we need them to be well and healthy.”

Since then, the list of states reporting carfentanil-related deaths includes (at least): Ohio, Florida, Illinois, Colorado, Wisconsin, Minnesota, Michigan, West Virginia, New Hampshire, and recently Virginia and Maryland. It has been suspected but not confirmed in other states.

In Ohio’s Hamilton county, which includes Cincinnati, law enforcement agencies got an average of 50 to 70 overdose reports a week in early 2016. When police noticed that carfentanil had arrived in the county, they saw a jump. In August, overdose reports rose to 175 to 200 in one week.

The Drug Enforcement Administration reports that all of the veterinarians and zoo keepers in the country need only around 18 grams of carfentanil a year to tranquillize large animals, including elephants. “If they don’t need very much of it to use on an annual basis to tranquillize big, large animals, then we humans don’t stand up at all,” Melvin Patterson, a spokesperson for the DEA told the Post.

Overdoses involving carfentanil can be reversed with naloxone, which blocks opioid receptors in the central nervous system. But, because carfentanil is so powerful, naloxone isn’t as effective and it may take several doses to revive someone who is overdosing.

Two months ago, Maryland Governor Larry Hogan declared a state of emergency in response to the opioid and, specifically, the heroin epidemic in the state. One of Hogan’s cousins died from a heroin overdose years ago. “With our new fight against carfentanil, which is 100 times more deadly than fentanyl, this emergency continues to grow,” he wrote in a Facebook post Thursday. “It is imperative that we raise awareness of just how deadly these drugs are.”