The company, which provides software to car dealerships, said its core dealer management system and digital retailing solutions had been restored. It said it also had tested and consulted with external third-party experts after the incident.

"We are continuing to conduct extensive tests on all other applications, and we will provide updates as we bring those applications back online," CDK said in an emailed statement to Reuters.

CDK's systems first went down around 2:00 a.m. EDT (0600 GMT) and some functions began to come back online by Wednesday afternoon, according to a report by  Bloomberg News.

The company was bought by investment firm Brookfield Business Partners in April 2022 for $6.41 billion in a cash deal that took private the last major publicly traded provider of software to auto dealers and manufacturers.

"We are aware of a reported CDK outage. We are currently evaluating any impact on our Ford Dealers," Ford Motor (F.N) told Reuters in an emailed statement.

General Motors (GM.N) and BMW <BMWG.DE> did not immediately respond to Reuters requests for comment sent outside regular U.S. business hours on whether the cyber incident had affected their dealerships.