With Hurricane Irma on track to slam into Florida this weekend or early next week, more and more units of the National Park System were closing in preparation.

Already closed by end of day Wednesday were Dry Tortugas, Biscayne, and Everglades national parks, along with Big Cypress National Preserve and DeSoto National Memorial, all in Florida, and Fort Pulaski National Monument in Georgia. On Thursday, the following parks were to close:

* Castillo de San Marcos National Monument in Florida

* Fort Matanzas National Monument in Florida

* Timucuan Ecological and Historic Preserve, which includes Fort Caroline National Memorial and Kingsley Plantation, in Florida

* Canaveral National Seashore in Florida

* Cumberland Island National Seashore in Georgia

* Fort Frederica National Monument in Georgia

* Congaree National Park in central South Carolina planned to close at noon on Saturday.

"The threat of direct hurricane impacts in Florida over the weekend and early next week has increased. Hurricane watches could be issued for portions of the Florida Keys and the Florida peninsula on Thursday," the National Hurricane Center said Wednesday evening.

There was no immediate word from Virgin Islands National Park on how it fared the storm.