The active transmission zone grew from 1.5 square miles to 4.5 square miles and consists of a large portion of the popular tourist destination, Florida Governor Rick Scott said in a statement on Friday evening.
Miami Beach Mayor Philip Levine told the Miami Herald that the city will begin truck-spraying of larvicide in the zone on Saturday.
"We have a serious problem," he told the newspaper. "Once again, we must take all reasonable and safe action to eliminate this. This is a problem."
The zone was expanded after the Florida Department of Health identified five cases in the area involving three women and two men who all experienced symptoms within one month of each other.
The cases bring the total of non-travel related Zika cases in Florida to 93 and in Miami Beach to 35, the governor said.
Three weeks ago, federal health officials warned pregnant women not to travel to Miami Beach because Zika has been shown to cause the severe birth defect known as microcephaly, a condition marked by abnormally small head size that can result in developmental problems.
The Zika virus was first detected in Brazil last year and has since spread across the Americas. It has been linked to more than 1,800 cases of microcephaly in Brazil.
Adding to concerns are current guidelines from the Centers for Disease Control and Prevention (CDC) that recommend men wait six months after being infected with Zika before trying to have children to avoid passing the virus to a pregnant partner through semen.
The governor also said on Friday he expects the Zika zone to be lifted on Monday in Wynwood where aggressive mosquito control and community outreach measures have been effective after several cases of Zika were confirmed recently in the neighborhood, north of Miami.
Scott also announced that he will authorize an additional $10 million in state funds to fight Zika and reiterated his call for Congress to provide more federal resources and funding.
"Every minute that passes that Congress doesn't approve funding means more time is lost from researching this virus to find a vaccine to help pregnant women and their developing babies," he said.