By Jessica Dye

NEW YORK (Reuters) - New York state's top prosecutor said on Thursday six companies have agreed to stop marketing products with claims that they can protect users from the mosquito-born Zika virus, just a day after his office sent them cease-and-desist letters.

New York Attorney General Eric Schneiderman sent the letters to seven companies on Wednesday, warning them to stop touting bogus “Zika-preventative” products, ranging from wristbands and patches using botanical oils to ultrasonic devices.

Of the seven companies cited Wednesday by Schneiderman, only the maker of the Neor Mosquito Repellent Bracelet was not mentioned Thursday as having complied.

“We won’t let fraudsters take advantage of a public health crisis, and this should serve as a warning to other companies who seek to engage in the same dishonest practices,” Schneiderman said in a statement Thursday. He said his office’s investigation into deceptive advertising practices related to Zika remain ongoing.

In announcing the cease-and-desist letters on Wednesday, Schneiderman said these primarily “fly-by-night” operations are trying to take advantage of public fear and concerns over Zika transmission. But the products they sell “simply don't work,” he said, and in some cases can even attract mosquitoes instead of repelling them.

Schneiderman encouraged consumers to stick with insect repellants registered with the U.S. Environmental Protection Agency, such as DEET.

The New York attorney general’s crackdown on Zika-related advertising claims comes amid growing concerns in the U.S. about the virus, which is spreading rapidly in the Americas.

New York officials have said 537 travel-related cases of Zika have been reported in the state. Florida authorities last week reported the first signs of local transmission of the virus in the continental U.S.

U.S. health officials have concluded that Zika infections in pregnant women can cause microcephaly, a birth defect marked by small head size that can lead to severe developmental problems.

The products targeted by the letters are sold primarily online, as well as in some local discount stores, Schneiderman said. The six compliant companies have removed misleading marketing claims and some have removed those products from online retailers altogether, according to the attorney general’s office.

(Reporting by Jessica Dye; Editing by Bernard Orr)