WASHINGTON — The Environmental Protection Agency warned Friday that disinfectants and sanitizers falsely claiming to protect against the coronavirus are flooding the market and threatened legal action against retailers that sell unregistered products.

A necklace containing chlorine dioxide, a bleaching agent, that supposedly sanitizes the wearer is among the bogus products, as is a sticker that claims to provide 30 days of protection against the coronavirus. A range of unregistered disinfectants, sprays, air purifiers and wipes also falsely assert they prevent infection from the virus.

A senior administration official said the agency is seeing a “huge” spike in such products, which have not been tested or registered by the E.P.A. While such products might not be harmful, the official said, they offer the public a dangerously false sense of protection that could deter social distancing and promote the spread of Covid-19, the disease caused by the coronavirus.

Andrew Wheeler, the administrator of the E.P.A., is expected to meet by teleconference with online retailers Friday morning to warn them against selling unregistered products that claim to be effective against the virus but do not have federal certification.