AAL American Airlines Group Inc

Hurricane Matthew strengthened Thursday and forecasters say it could further intensify as it heads toward Florida's Atlantic coast.

The National Hurricane Center advised at 5 a.m. EDT that the category 3 storm had winds near 125 miles an hour, up from 115 miles an hour Wednesday night.

It is moving northwest with the eye expected to pass near the northwestern Bahamas early Thursday morning and Grand Bahama Island late in the day. The storm is forecast to strengthen, possibly to a category 4 hurricane, as it approaches Florida's coast Thursday night through Friday night, the center said.

The center predicted heavy rain, strong winds and storm surges along the U.S.'s southern East Coast. A hurricane warning, already in effect for much of Florida's eastern coast, was extended northward to Altamaha Sound, Ga., and a hurricane watch has been extended northward to South Santee River, S.C.

At least 11 deaths have been blamed on the storm during its weeklong march across the Caribbean, five of them in Haiti, according to the Associated Press.

Southern U.S. states took no chances. Governors of Florida, Georgia and the Carolinas declared states of emergency.

Florida Gov. Rick Scott ordered state offices to be closed on Thursday and Friday in 26 counties and urged people in the path of the storm to leave the coast as early as possible. "I encourage everyone to prepare their homes, check on family and friends and evacuate if in an evacuation zone," he said Wednesday. "This storm is deadly and everyone has to take this seriously."

Florida residents for days have been stocking up on staples and hurricane supplies, and many grocery and hardware stores have empty shelves. By Wednesday evening, boats in many marinas were hauled away and the windows of many buildings were covered with plywood.

The Port of Miami closed its cargo-handling Pomtoc and South Florida Container Terminals facilities to vessels and trucks on Wednesday and the Miami city government shut down the tunnel highway entrance to the port, according to statements released on Twitter.

Mass evacuations of coastal communities in South Carolina were set to continue, Gov. Nikki Haley said at a news conference Wednesday morning. She closed government offices and canceled schools across much of the state, and urged people leaving the coast to drive at least 100 miles inland.

She ordered evacuations in the southern part of the South Carolina coast to begin later Wednesday, and those along the northern part of the state's coast to begin Thursday. About 250,000 people may have to relocate, she said.

U.S. airlines widened the lists of airports that might be affected by the storm, while working to restore normal service in the storm's aftermath in the Caribbean.

American Airlines Group Inc. said Wednesday it would halt all flights from arriving at its Miami hub on Thursday, along with the airports in Fort Lauderdale and West Palm Beach.

The company expected to have "limited departures" from the three airports until about noon EDT on Thursday, after which flight activity will cease, a spokesman said.

American later added the Orlando, Fla., airport to its list for planned cancellations. The carrier said it would scrub all arrivals and departures there after 5:30 p.m. EDT on Thursday, will operate no Orlando flights Friday, and plans to resume limited service Saturday morning.

Susan Carey and Paul Page contributed to this article.

Write to Cameron McWhirter at cameron.mcwhirter@wsj.com

(END) Dow Jones Newswires

October 06, 2016 08:05 ET (12:05 GMT)

Copyright (c) 2016 Dow Jones & Company, Inc.