Hundreds of flights were grounded at two major Chicago airports Friday, snarling air transit for hours after a fire at an air traffic control facility, officials said.
Air transit into and out of the city's bustling O'Hare International and Midway airports was completely shut down as a result of the blaze at the Federal Aviation Administration's facility in the town of Aurora, Illinois, which news reports said appears to have been deliberately set.
News reports said firefighters arriving at the facility early Friday found an adult male suffering from an apparent self-inflicted wounds.
Local media said the man is being treated at an area hospital for his injuries and for smoke inhalation.
Valerie Jarrett, a senior adviser to President Barack Obama, said federal authorities had joined the probe in the fire, as the resulting delays and cancellations threatened to snarl air transit not just in the immediate region, but across the country.
"An investigation is under way between federal, state, and local authorities and we will be hearing more from them as they have results," Jarrett, who like Obama hails from Chicago, told MSNBC television.
Jarrett warned that with air transit disrupted at one of America's busiest airports, "there is going to be a lot of inconvenience and it's very, very frustrating."
An online flight tracking website, Flightaware, said shortly after 1600 GMT that 1250 flights had been canceled at the two airports -- about half their entire daily schedule -- creating transit chaos that could take hours, even days, to unsnarl.
"Chicago airspace is almost completely empty due to fire at Aurora Air Traffic Control," said another flight tracker, the website Flightradar24.
"It is still not known when traffic can resume," Flightradar24 said.
The FAA released a statement Friday saying that the fire occurred shortly before 6 am (1100 GMT)in a basement telecommunications room at its Chicago En Route Center.
The aviation radar facility was evacuated and joint investigations were being carried out by the Federal Bureau of Investigations, the Bureau of Alcohol, Tobacco and Firearms and local agencies, as well as the FAA itself.
"Flights that were already in the air destined to the Chicago area were allowed to continue at a reduced rate, or proceed to an alternate destination," the FAA statement said, adding that it is working with airlines to minimize the inevitable travel chaos.
Authorities said some operations of the FAA's Aurora center, which is responsible for guiding high-altitude air traffic into and out of the airports, would be taken over by other air traffic sites in the region.
O'Hare, the second-largest airport in the United States, handles more than 67 million passengers each year.