Federal regulators fired a shot across the bow of a host of telemarketing firms on Friday, warning them against propping up illegal robocalling scams seeking to cash in on the coronavirus pandemic.

Staff at the Federal Trade Commission “have reason to believe that one or more of your customers may be involved in such illegal telemarketing campaigns,” the FTC wrote in letters to nine call center companies dated March 27. “Many of these robocalls prey upon consumer fear of the pandemic to perpetrate scams or disseminate disinformation.”

Government agencies and private watchdog groups have tallied thousands of such robocalls, which attempt to bilk consumers with offers of discounted health insurance and free coronavirus testing kits. They represent one of several new targets of government-wide efforts to crack down on scammers using the virus outbreak to try to cash in.

“There already is a high level of anxiety over the potential spread of coronavirus,” FTC chairman Joe Simons said in a statement on Friday’s warning letters. “What we don’t need in this situation are companies preying on consumers by promoting products with fraudulent prevention and treatment claims. These warning letters are just the first step. We’re prepared to take enforcement actions against companies that continue to market this type of scam.”

The Federal Communications Commission is also monitoring coronavirus-related telemarketing scams. It’s even set up a website where visitors can listen to recordings of scam phone calls and find information on weeding out and reporting the scammers.

“We are aware of and concerned by scam calls and texts trying to prey on consumers during this crisis,” an FCC spokesperson told The Daily Beast last week. “We hope consumers will use extreme caution and will refrain from providing any suspicious callers or texters with any personal or financial information. As we review consumer complaints about specific scam patterns, we will work to help consumers stay informed.”

Archives of coronavirus-related robocalls set up by the FCC and privately run websites such as NoMoRobo and YouMail reveal some templates for the various scammers trying to capitalize on the outbreak. Many offer free coronavirus testing kits. Others hawk health insurance or various Medicare supplemental plans. Some even impersonate federal agencies themselves—”Dear citizen, this is United States Department of Health,” one recorded caller says, “if you wish to talk to a health advisor right now please press one.”

Federal law allows the FTC to seek civil penalties against companies engaged in illegal robocalling, which includes any automated marketing calls that make “a false or misleading statement to induce any person to pay for goods or services or to induce a charitable contribution.”

The novel coronavirus has dominated headlines for weeks now, and fears about its spread provide fertile ground for scammers looking to market fake health care products. Nearly as concerning as overt efforts to extract money from unsuspecting consumers is the disinformation about the virus that these appeals often spread.

The FTC and the Food and Drug Administration have also gone after homeopathic medicine proponents and other “natural” wellness websites of late over false claims that their products can cure or mitigate the coronavirus. The agencies’ highest profile target to date is Jim Bakker, a televangelist who has promoted fabricated silver-based “cures” to the virus on his popular talk show.

The state of Missouri is now suing Bakker to prevent him from making such claims. A post on his website headlined “Covid-19 Coronavirus, building immunity, staying healthy and the benefits of Silver Solution” is no longer publicly accessible.

Others targeted in the federal government’s crackdown on such misinformation have been more obstinate. After receiving a warning letter on March 6, the website Herbal Amy, a natural medicine website that had promoted various plant-based coronavirus remedies, removed the post flagged in the letter from its website. But two weeks after the letter was sent, Herbal Amy’s Facebook page doubled down on the underlying claims.

“Cinchona [tree bark] is the only economically practical source of quinine, a drug that is still recommended for the treatment of malaria and now Coronavirus,” the page read. “If anyone tells you that herbs don't work, they are either ignorant to facts or lying.”

Additional FTC action against other sources of such misinformation indicates that it hasn’t slowed up since the commission went after Bakker, Herbal Amy, and five other companies earlier this month. Last week, the FTC sent two more warning letters to companies engaged in similar practices. One of them, corona-cure.com, appears to have removed its website entirely since receiving a warning letter on Thursday. Postings on another website, carahealth.com, claiming that the virus can be addressed through “Chinese medicinal herb extracts” remained publicly accessible on Sunday afternoon despite a warning letter also sent on Thursday.

Though few news consumers have likely come across sources of information as obscure as those, such misinformation is not confined to fringey alternative medicine Facebook pages. Some large, widely read news outlets have peddled similar alternative medicine and homeopathic remedies.

The health vertical on conservative news giant Newsmax is a hotbed of such claims. As the coronavirus spread, it published debunked claims that originated on an alternative medicine website that regular doses of vitamin C could slow or entirely stop the spread of the virus.

Newsmax has promoted other dubious remedies as well. “Zinc Lozenges May Help Combat Coronavirus” declared the headline of a March 17 story that linked to a McGill University blog post that found the exact opposite. A story in its health section a week later promoted “traditional Eastern medicine remedies” as a coronavirus treatment.

Newsmax has not been singled out by federal health authorities for spreading false information about coronavirus treatments. But as it runs those stories, it’s also served readers with ads that warn of impending financial disaster due to the virus. That was enough to earn a stern warning from the Federal Deposit Insurance Corporation, which demanded that the site stop claiming, falsely, that banks might soon raid Americans’ retirement accounts.

“The FDIC has repeatedly sought to contact Newsmax to stop publishing these false ads and to issue a correction to its readers,” the agency wrote in a statement. “The media organization has not responded to these requests.”