Authorities evacuated thousands from a Chicago-area hotel Sunday after guests complained that a noxious odor was spreading.
 
Now detectives are investigating, and police say it appears that "an intentional act" was behind high levels of chlorine gas that forced the evacuation at the Hyatt Regency O'Hare in Rosemont, Illinois, early Sunday morning.
 
The hotel was hosting the Midwest FurFest, a convention where many attendees don animal costumes and "celebrate furry fandom, that is, art, literature and performance based around anthropomorphic animals," according to the event's website.
 
Read more: CNN