(CNN) -- Severe thunderstorms moved through southern Wisconsin and northern Illinois Monday, bringing reports of tornado touchdowns and significant damage.
At least three children in Caledonia, Illinois, about 15 miles northwest of Rockford, were injured when the bus in which they were riding rolled over, according to the National Weather Service. The extent of their injuries wasn't immediately known.
The worst of the storm hit around 3 p.m. (4 p.m. ET), knocking down power lines along a country road and hitting the village of Caledonia especially hard, said Boone County, Illinois, emergency management director Sandra Rogers.
Heavy winds destroyed the Caledonia town hall and one home, damaged another three homes and knocked out power to more than 500 residents, Rogers said.
Power lines were down near Caledonia, and additionally one business was "almost completely destroyed" and a damaged grain silo was leaking grain, the weather service said.
Heavy winds Monday afternoon also struck the Wisconsin town of Union Grove, about 30 miles south of Milwaukee.
Some 36 residents of an assisted-living facility there had to be moved after heavy winds caused structural damage and forced the facility to rely on generator power, said Lt. Dan Klatt of the Racine County Sheriff's Office. The storm also blew the roof off a building onto a nearby residence and damaged Union Grove's sewage treatment plant, he said.
The winds also peeled shingles from houses and downed power lines, according to Klatt, saying he expected power to start returning around 10 p.m. He said he could not confirm that a tornado had struck, while adding that the damage was largely confirned to a path near highways 11 and 45 in the county.
"We're surprised to by a storm of this magnitude: Typically, we don't see tornadoes in late November," Klatt said. "We just want to get people back to their homes safely."
Union Grove firefighter Kris Nissila said heavy winds overturned several semi-trucks, caused "numerous gas leaks," and "we have multiple buildings that aren't there any more."
"Right next to my house, there was a garage that was gone," he said.
Additionally, at least two homes were also damaged by possible tornadoes near Walworth, Wisconsin, the National Weather Service said. That agency also reported another twister touched down in Lawrence, Illinois, like Rockford located northwest of Chicago.
In addition to tornado-like winds, the storm at times produced hail up to 2 inches in diameter, wind gusts up to 75 mph and dangerous cloud-to-cloud lightning.
The inclement weather wreaked havoc with travel: As of 8:30 p.m. Monday, delays at Chicago's O'Hare airport averaged an hour and 43 minutes.
The worst of the storm appeared to have passed by 8 p.m. (9 p.m. ET), though thunderstorms prompted the service to warn of a "severe weather threat" for much of central Illinois. In addition, "significant snow" was forecast beginning Monday night and into Wednesday for much of north central and central Wisconsin.
CNN's April Williams, Leslie Tripp and Greg Botelho contributed to this report.