A tornado touched down near Chicago’s O’Hare International Airport, prompting passengers to take shelter and disrupting hundreds of flights. There were no immediate reports of injuries.

A confirmed tornado was on the ground around 7 p.m. Wednesday, according to the National Weather Service in Chicago.

By 8 p.m. the weather service said the Chicago forecast area was “currently tornado warning free.” The storm moved into Michigan before passing through the state and into Canada early Thursday. Tornado watches that were in effect for parts of Michigan, Indiana and Ohio all expired.

Video from TV stations showed hundreds of people taking shelter in an O’Hare concourse. Some 173 flights departing the airport were canceled and more than 500 were delayed, according to the flight tracking service FlightAware.

The National Weather Service had issued two tornado warnings for Chicago Wednesday evening. Tornado sirens sounded warning people to find shelter

The weather service quoted an unidentified emergency manager as saying a roof was blown off in the community of Huntley in McHenry County northwest of Chicago. Huntley Battalion Chief Mike Pierce told ABC-7-TV that firefighters and other emergency services were responding to downed power lines, trees and tree branches, and that power outages had been reported. Building damage appeared to be concentrated around two apartment buildings, he said.

Over the years many tornadoes have struck in the Chicago metropolitan area, and several have hit within the city limits of Chicago, according to the National Weather Service. Between 1855 and 2021, the weather service recorded 97 significant tornadoes in the Chicago metro area.

The deadliest formed in Palos Hills in Cook County on April 21, 1967. The twister traveled 16 miles (26 kilometers) through Oak Lawn and the south side of Chicago, killing 33 people, injuring 500 and causing more than $50 million in damage, according to the weather service.