Evidence of local Zika virus transmission in Miami Beach is reported to have been found by Florida health officials.

The discovery at one of the world’s most popular tourist destinations opens a new front in the fight against the mosquito-borne virus, a source familiar with the investigation told Reuters.

A handful of Zika cases have been identified and health officials are deciding which area or areas to include in any updated travel guidance, the source said.

An announcement is expected to be made as early as today (Friday).

The prospect of the virus spreading to the tourism-dependent Miami Beach area is likely to alarm tourism officials.

Last year, some 15.5 million people spent at least one night in Greater Miami and the beaches, generating nearly $24.4 billion in direct expenditures, according to the Greater Miami Convention & Visitors Bureau. More than 48% of all visitors stayed in Miami Beach.

Miami Beach mayor Philip Levine said yesterday that state and federal health officials have yet to conclude the tourist hotspot is the latest area where Zika has been transmitted.

“We don’t know the exact link, one could be a tourist, one could be someone who may have worked on Miami Beach,” he said. “If it was confirmed we’d be able to talk about that, but it’s not.”

Levine said health department investigations are ongoing, and a determination could come as soon as Friday.

There have been 35 cases of likely local transmission in the state, including the two new cases announced on Thursday.

A spokeswoman for Florida’s health department, Mara Gambineri, said it believes active transmissions are still only occurring in a small area in the Wynwood area of Miami but acknowledged two new Zika cases outside that area.

The virus, which has spread rapidly through the Americas since it was first detected in Brazil last year, can cause the rare birth defect microcephaly, marked by abnormally small heads and developmental problems.