Scammers are knocking on people's doors and claiming to be part of the official response to the coronavirus, police in New Jersey have warned.
The people could then try and take advantage of anxiety around the spread of the disease to sell products at inflated price or otherwise try and scam anyone in the house, authorities warned.
They warned people that the Centers for Disease Control and Prevention was not sending people to knock on doors to "conduct surveillance".
Anyone doing so should not be let into the house or spoken with, officials warned.
Two townships in New Jersey have given warnings about the behaviour, though it is unclear how widespread it is.
Police in one township, Nutley, said they were "advising residents of a safety issue" and said that they had received information about "individuals going door to door claiming to be from the CDC".
"The CDC is not deploying teams of people going door to door asking questions. People should be warned to not let them in their homes or to speak with them," wrote director Alphonse Petracco and chief Thomas Strumolo.
In another township, Moorestown, the police department said that "unfortunately there always seems to be fraudsters & scammers trying to take advantage of a public health event". It said it was sharing information from the New Jersey Department of Health.
It urged people to contact local authorities "if you find that a merchant has inflated the cost of products taking advantage of the public health event".
"The CDC is not deploying teams of people to go door to door to conduct surveillance," the police department wrote. "People should be warned to not let them in their homes or to speak with them.
"They are imposters. Contact local law enforcement if this activity is reported in your municipality."