MIAMI — With the nation’s first suspected local outbreak of Zika infection under investigation in South Florida, the Food and Drug Administration on Wednesday requested that all blood banks in Miami-Dade and Broward counties stop collecting immediately until donations can be tested for the virus.

Blood banks in the two counties said they would begin screening donations for Zika virus using an FDA-approved test beginning Friday, but it was unclear whether or when collections in South Florida had ceased Thursday.

OneBlood, a nonprofit with six centers in Broward and five in Miami-Dade, issued a statement that the agency received notice of the FDA’s request only after they had already begun collecting Thursday.

“OneBlood is working as quickly as possible to comply with the FDA’s request,” said the statement. It added that earlier in the week the agency suspended collections in “a number of areas in South Florida” where the suspected cases are under investigation.

Area hospitals were not expected to be impacted by the temporary suspension of blood collection. Jackson Health System, Miami-Dade’s public hospital network, had not received notice that blood supplies would be limited, spokeswoman Jennifer Piedra said.

“We do not anticipate it will impact operations at our hospitals,” she said.

One Blood, which supplies blood to more than 200 hospitals in most of Florida and parts of Georgia, Alabama and South Carolina, said all of the agency’s sites would begin testing for Zika on Friday.