NAGS HEAD, N.C. -- Officials in North Carolina estimate more than 10,000 people have left the Outer Banks as Hurricane Maria moves closer.

Dare County Emergency Management Director Drew Pearson said Tuesday morning that it's impossible to get exact figures on how many people evacuated Hatteras Island after they were ordered to do so.

Pearson said officials think between 10,000 and 12,500 people have left the island ahead of the storm. Hatteras has a year-round population of about 500 people, who are not required to leave.

Pearson said the worst conditions were expected Wednesday into Thursday morning.

Hyde County officials said Monday they thought about 700 visitors would leave because of the evacuation ordered for Ocracoke Island. Ocracoke has a population of about 1,000 residents.

A tropical storm warning is in effect from Morehead City to the North Carolina-Virginia state line.

Officials say the biggest threat is the storm surge which is expected to be 1 to 2 feet -- causing flooding along some major roads.