A viral social media trend has sparked a rash of car thefts in cities across the U.S.

The now viral videos, seen on TikTok and other social media platforms, demonstrate how a person can start a car without a key by using only a screwdriver and a USB phone charger to hot-wire automobiles, with some Kia and Hyundai models particularly vulnerable.

In Cook County, Illinois, which includes Chicago, the state's most populous city, local authorities say they've seen a 767% increase in Kia and Hyundai car thefts since 2021. Since July 1, the county has received 642 reported Kia and Hyndai vehicle thefts, a dramatic rise from last year's 74 reported thefts.

“This is an extremely concerning trend and the public needs to know so they can be vigilant in protecting themselves,” Cook County Sheriff Thomas J. Dart said in a statement.

The hack only works on cars with keys that don't have engine immobilizers, a type of anti-theft technology that uses a computer chip to help an engine recognize a corresponding key.

VIDEO: Car thefts increase amid social media trend, police say
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Authorities are blaming a social media challenge for an alarming rise in car thefts.

Hyundai told "Good Morning America" the TikTok videos target Hyundai models that were made before November 2021 and the automaker plans to roll out security kits for those models starting in October.

In a statement, the company said it will work with police departments to "make steering wheel locks available for affected Hyundai owners."

Police in Park Forest, Illinois, about 35 miles south of Chicago, said in a social media post that the cars most likely affected are select 2011-2021 Kia and 2015-2021 Hyundai models.

"Vehicles in those model years that are not equipped with a push-button start are more easily started without a key (hotwired) than cars from other manufacturers," the department said in a July 30 Facebook post.

Some Kia and Hyundai owners have since filed a class-action lawsuit in Missouri and Kansas, as reported by ABC affiliate KMBC.

In a statement to ABC News, TikTok said it "does not condone this behavior, which categorically violates our policies and will be removed if found on our platform."

To prevent a car theft, the National Insurance Crime Bureau recommends using visible or audible devices, such as steering wheel locks, brake locks, wheel locks, steering column collars, audible alarms and theft deterrent decals as part of a multi-pronged approach to discourage would-be thieves. Law enforcement officials are also reminding drivers to park in well-lit areas and public locations.

Editor's Note: This article has been updated to include comment from TikTok. Some language has also been changed to reflect that the circulation of this video has not been restricted to just one social media platform.