The gator - estimated to be between 4 and 5 feet long - was first spotted at the Humboldt Park Lagoon on the city's West Side early Tuesday by visitors who spotted the reptile's head poking out of the water.
Several hours later, Chief Communications Officer Anthony Guglielmi confirmed that authorities spotted the gator and that a state reptile specialist put the alligator at somewhere between four to- five feet long.
Police said they are still investigating.
Richard Crowley, president of the Chicago Herpetological Society, told CNN he believes the reptile was brought to the lagoon, possibly by someone who owned it illegally (it's illegal to own an alligator in the state of Illinois).
How exactly did an alligator get in Humboldt Park?
It "will probably be scared and try to hide", she added.More news: Trent Boult craves revenge and hopes for Australia in World Cup final
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Horst-Ruiz said she was initially in disbelief upon hearing a man say he spotted the animal as she readied for a Sweet Sixteen photoshoot in the park, she told Block Club Chicago.
"It's only been in here a day or two at the most", "Alligator Bob" continued. "He's gonna be looking for a better place to sleep".
As of Wednesday morning, the wild animal was still at large in the park, despite humane bait traps filled with fish and chicken set up throughout the lagoon.
Guglielmi assured the public that the gator will be "humanely" captured before moving the animal to a nearby zoo for a "veterinary evaluation", according to Fox News.
Strangely enough, this isn't the first alligator to grace Chicago waters. In 2010, he also helped trap a gator in the North Branch of the Chicago River, the Chicago Tribune reported. But police are asking people to stay out of the water.
Another witness said he "clearly" saw the gator with its eyes above the water and speculated that the animal had been ditched there by its previous owner. He works with Chicago officials to capture exotic animals, according to Crowley.