People dressed in furry animal costumes were rushed to the hospital on Sunday morning after a deliberate gas leak at the Hyatt hotel in Rosemont, Chicago caused the guests to become sick.

According to the Rosemont Public Safety Department which sent first responders to the hotel located at 9300 West Bryn Mawr Avenue, high level of chlorine gas was spreading on the ninth floor, causing 19 guests attending the yearly weeklong Midwest Furfest to feel dizzy or nauseous.

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The responders ordered the immediate evacuation of all hotel guests to nearby facilities such as the Donald E. Stephens Convention Center where a dog show was being held, making some of the convention participants think it was still part of the fun.

A hotel guest told Chicago Tribune many of those evacuated thought someone pulled the fire alarm since such pranks usually happen at events like the FurFest.

After the hotel was decontaminated, the guests were allowed to return to Hyatt and finish the last day of the Furfest which attracts thousands of attendees yearly to celebrate art, literature and performance that are based around anthropomorphic animals.

These are characters from movies, TV shows, comic books and video games, while some are characters created by the participants such as a purple furry dragon.

The police said that hazardous materials technicians traced the source of the leak to powdered chlorine placed at the ninth floor's stairwell, strengthening he suspicion that the leak was a deliberate effort to sabotage the event.

Thoughts of blaming anti-fur groups for the gas leak were banished by participants since all of them used fake fur for their costumes. The Rosemont police is still investigating which group is behind the sabotage.

Meanwhile, the Furfest organizers and Hyatt said they won't refund since the incident was "an unforeseen criminal act," and the activities for Sunday would go on as scheduled.

"We ask you to continue to be patient, and remember that the volunteers who make Midwest FurFest happen intend to give 100% to make sure that the fun, friendship, and good times of Midwest FurFest 2014 overshadow last night's unfortunate incident," the organizers said in a statement.

Tagsmidwest furfest, Gas Leak, hyatt regency