© AP/AP This undated photo provided by U.S. Centers for Disease Control and Prevention shows CDC's laboratory test kit for the new coronavirus. (CDC via AP)

For police departments, there has been no greater, or worse, home for the law enforcement equivalent of dad jokes than Facebook.

They have issued arrest warrants for Elsa from “Frozen” for bringing a cold snap to their communities, or have “canceled” crime for a night because of frigid temperatures. Other times they have joked about fake-news “meth alligators."

Now, some are joking about coronavirus — warning that the potentially deadly disease may have tainted the local meth supply at a time when nearly 3,000 people worldwide have died and the country is preparing for an outbreak.

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“WARNING: If you have recently purchased Meth, it may be contaminated with the Corona Virus,” wrote the Merrill Police Department in Merrill, Wis., in a Wednesday Facebook post about the disease. “If you’re not comfortable going into an office setting, please request any officer and they’ll test your Meth in the privacy of your home. Please spread the word! We are here for you!”

It was one of several police departments nationwide to push out the hoax, apparently in pursuit of laughs and possibly even the rare arrest. It generated mixed reactions, some seeing it as funny, others as deplorable, fueling coronavirus fears through fake public service announcements on official channels.

“I would rather not see police departments making ‘jokes’ like this online or posting false information about a pandemic that is already being treated cavalierly by the executive branch,” one woman said in a comment on the Merrill Police Department’s post.

“shut up snowflake,” someone replied.

Departments in St. Francis County, Ark., Johnson City, Tex., Tavares, Fla., and Decatur County, Kan., have all blasted out the warning, in some cases grabbing straight-faced headlines from local TV news outlets that ran the story like a police news release without a hint of skepticism. “Texas police say local meth is contaminated with coronavirus, offer to test it,” read one.

Public health experts who spoke with The Washington Post said they envisioned health agencies in these communities reading the tongue-in-cheek posts with raised eyebrows.

“That’s pretty extraordinary,” Stefano M. Bertozzi, a professor at the University of California at Berkeley’s School of Public Health, said of the viral police joke.

“This is a time when people need to be taking public health authorities very seriously,” he added. “They’re undermining their credibility that will be very much needed if and when an epidemic comes to their community.”

This isn’t the first time local police have used a viral disease outbreak to lure unwitting users into giving up their drugs through hoax scare tactics. The last time, not everyone got the joke.

During the Ebola outbreak in 2016, the Granite Shoals Police Department issued a similar fake PSA. “If you have recently purchased meth or heroin in Central Texas, please take it to the local police or sheriff department so it can be screened with a special device,” the since-deleted post said, according to the San Antonio Express-News. “DO NOT use it until it has been properly checked for Ebola contamination!”

One person, actually fearing her drugs could be contaminated, reportedly showed up at the police station to answer the Facebook post and have the drugs tested. She was arrested and charged with possession of less than one gram of a controlled substance, the Express-News reported.

That was another joke for the police, who called the defendant the “winner” of the contest. “Please continue to report any possibly tainted methamphetamine or other narcotics to the Granite Shoals Police Department,” according to the post archived by Ars Technica.

Swift backlash followed, leading the Central Texas police department to defend itself in a follow-up post, railing against the news media that “only wants to show law enforcement at our worst times and not our best,” and saying it was an attempt to humanize the police department through humor, according to the archived post.

Ted Gideonse, a professor at the University of California at Irvine’s Program in Public Health, who specializes in substance abuse and public health ethics, said he doubts many would fall for the trap. But the problem with fake news coming straight from a police department is that these “stories end up getting lives of their own,” existing “in the underbelly of the Internet where people don’t actually question things.”

“The last thing we need to do is have people in the local public health departments having to deal with disinformation campaigns coming from their actual colleagues as opposed to social media or bad TV journalism,” he said.

After the reaction to its post, the Merrill Police Department said in an update on Thursday that it realized their coronavirus-related hoax had sparked “a lot of opinions, emotions, and touched some tender spots.” The department said that, if someone were to turn themselves in due to its post, the police would view it as a positive step forward for that person.

“We will take those easy grabs at removing poison from our community whenever we can,” the post said. “That is our role which we un-apologetically must fulfill. It is our hope that an arrest would be the positive catalyst someone may need to start recovery.”

In a statement to The Post, Johnson City, Tex. Police Chief Ross Allen said his department had copied the post from other police departments and that it was “meant to be satirical.”

“As for criticism, people are entitled to their opinion,” he said.