Authorities briefly reopened two highways crossing north Florida into Georgia on Sunday before dense wildfire smoke forced them to again halt traffic, while hundreds of Florida residents waited to return to their threatened homes.

Officials said Sunday that the wildfire that had raced through the Okefenokee Swamp in southeast Georgia and into Florida had charred more than 233,700 acres — or about 365 square miles — since it was started by lightning a week ago.

Officials warned that storms in the forecast Sunday could bring either much-needed rain or lightning.

Authorities reopened 90 miles of Interstates 75 and 10 for a couple of hours Sunday morning after wind helped push the heavy smoke away from the highways. But they were later forced to close 35 miles of I-75 from the Florida-Georgia state line to Lake City, Florida, as well as a 40-mile stretch of I-10 in Florida, from Live Oak to Sanderson.

A 15-mile stretch of I-75 from Valdosta, Georgia, to the Florida state line remained open Sunday.

About 570 residents were not being allowed to return to 150 homes evacuated between I-10 and the Florida-Georgia state line.

The fire started May 5 in the middle of the Okefenokee National Wildlife Refuge. It took just six days to grow larger than another wildfire that has burned nearly 121,000 acres of Georgia forest and swampland over more than three weeks. The small fire was started by a tree falling on a power line.

The Okefenokee National Wildlife Refuge and Georgia's Steven C. Foster State Park inside it remained closed.

Haze from the fires had traveled as far south as the Miami area, about 340 miles away.

Elsewhere, a blaze feeding on drought-stricken forest in northern Minnesota was only 15 percent contained as of Sunday morning. Meteorologists said there was a 40 percent of thunderstorms Sunday. They could produce the first significant rainfall in the parched area in almost a week, but the hope of rain was outweighed by the threat of wind gusting to 25 mph.

"We don't think the rain is going to help us a whole lot," said Mark Van Every, a spokesman for the firefighting effort.

The fire had closed about half of the 57-mile-long Gunflint Trail, a key route from Grand Marais into the Boundary Waters Canoe Area wilderness that is dotted with resorts and lake homes.