Users who attempted to access the firm's mobile app to book a vehicle have been met with a notice which says that services are not now available and the company will "provide an updated as soon as possible".
Users attempting to use the service in Chicago Wednesday afternoon were shown an error message saying it is temporarily paused.
"We are working with law enforcement to neutralize a fraud issue", the company wrote in a tweet.
An app-based rental auto company has suspended service in Chicago after more than 100 vehicles were stolen through misuse of its mobile application.
Handsome and warmer weather for the holiday weekend
Extensive mist and fog on Saturday night, with patchy drizzle in parts of the west and north in near calm conditions. However it will remain warm and dry in many areas with hazy sunshine developing through the Munster and Leinster.
"The Chicago Police Department is working with the company to determine whether there any other vehicles whose locations can not be accounted for", read a statement issued to CBS 2. "There was no 'hack.' No personal or confidential member information has been compromised".
'Out of an abundance of caution and safety for our members we are temporarily pausing our Chicago service, ' a car2go spokesperson told WBBM-TV. CBS Chicago is reporting that some of the missing cars have been used to commit crimes. Check back for more updates. Half of the missing vehicles are Mercedes-Benz models such as the CLA-class sedan and the GLA-class subcompact SUV, while others include the tiny Smart Fortwo city auto. Users locate their cars via the company's mobile app and then simply park them when they are done. Multiple vehicles had been recovered, police said at the time. Mike Silverman, a Share Now spokesman, declined to comment on details of the incident due to there being an ongoing police investigation.
A question from Mashable about what type of cars were stolen - Car2Go offers Mercedes-Benz in addition to smart cars - went unanswered by the company spokesperson.
So far, 21 people have been charged with misdemeanor criminal trespass to vehicle, and one of those individuals faces an additional felony charge for financial identity theft. "This is an instance of fraud, isolated to Chicago".