(CNN) -- Severe weather tore across central Florida on Thursday, causing damage and spawning an apparent tornado in Tampa, the National Weather Service said.
A heavy storm with strong winds hit the Sun 'n Fun aviation fair at Lakeland Linder Regional Airport, causing "extensive minor damage and reports of minor injuries," but "all persons so far have been accounted for," said Sgt. Terri Smith of the Lakeland Police Department.
The National Weather Service had reported a building collapse that trapped 70 people at the airport, but that report was false, Smith said.
The Sun 'n Fun International Fly-In & Expo is a six-day aviation-themed festival that provides the primary source of funding for Sun 'n Fun, a nonprofit organization, and its wholly owned subsidiary, the Florida Air Museum.
Greg Lane, a Sun 'n Fun volunteer who is working with a low-power AM radio station at the airport, said the "sky went from gray to black to bluish green" as the storm rolled in.
"You couldn't see the tents that were 50 feet across the drive from us," he said.
The state's emergency management office said it has deployed personnel to the airport and is monitoring the situation, according to spokeswoman Melanie Motiska.
In Tampa, meanwhile, an apparent tornado touched down, and parts of Hillsborough County were under a tornado warning that the weather service issued at 11:51 a.m. The warning covered parts of Hillsborough and Polk counties.
Tampa Mayor Pam Iorio said there has been some damage to residences and businesses in the city as a result of "very, very severe weather."
However, she said, there have been no injuries, and "I think we're faring well." She said trees, including huge oaks, have been upended and power lines have been downed.
The fire department has been at the scene of every structural damage incident, Iorio said. She added that there might be more severe damage outside the city.
Iorio added that since Wednesday, media reports had warned residents that "today's the day to stay inside" because of bad weather.
"It's going to be a big system for the rest of the day," said CNN meteorologist Chad Myers, referring to the low-pressure system and cold front that developed over the Gulf of Mexico and moved east across Florida. "You need to get inside your home and away from the glass."
The storm damaged about 25 homes in Hillsborough County, Sheriff's Office spokeswoman Debbie Carter said.
Severe thunderstorm and tornado warnings have been issued across north and central Florida and will remain in effect until 8 p.m. ET, emergency spokeswoman Motiska said.
Additional strong to severe thunderstorms with damaging winds, hail, heavy rain, lightning and isolated tornadoes are also possible through the evening.
A photo on the website of Bay News 9 showed an overturned small airplane at the St. Petersburg/Clearwater airport. The affiliate also broadcast images of damaged street signs and billboards as high winds swept through the area.
CNN's Joe Sterling contributed to this report.