Work has begun to restore systems used by 15,000 auto dealers nationwide, which has been the subject of a cyber hack and ransom demand, Reuters reported Sunday.

A group that says they hacked software company CDK Global is demanding tens of millions of dollars in ransom, Bloomberg reported on Saturday.

CDK, which provides software to car dealerships in North America, intends to pay the ransom but discussions are subject to change, according to Bloomberg's report, which cited a person familiar with the situation.

The source said the group behind the hack is believed to be based in eastern Europe, Bloomberg reported.

USA TODAY has reached out to CDK Global for comment.

CDK cyberattack:Hackers force shutdown of car dealership software systems after cyberattack

System shutdown upends dealership operations

The CDK cyber outage affects software management tools and has upended operations at car dealerships across the U.S.

The company shut down most of its systems "out of an abundance of caution" for customers on Wednesday, CDK spokesperson Lisa Finney said. The company said it restored some systems later that afternoon, before closing them again when additional cyberattack occurred, according to a letter sent to customers.

"Out of continued caution and to protect our customers, we are once again proactively shutting down most of our systems," the letter said. "We are currently assessing the overall impact and consulting with external 3rd party experts."

The company did not originally share an estimated time frame as to when systems would be back up and running. Dealerships continued to report issues with CDK systems on Friday and Saturday. On Sunday, CDK in an emailed statement to Reuters, said it expected the restoration process to take "several days."

In Detroit, the hack and shutdown has caused dealers to move to old-fashioned paper sales records, the Detroit Free Press reported. That included taking documents to the Secretary of State in person to process license plates.

CDK Global works with 15,000 retail locations 

Finney did not respond to questions on how many dealerships were impacted, but CDK’s website says the company works with more than 15,000 retail locations across North America.

One of the leading providers of cloud-based software to dealerships in the country, CDK's software helps dealerships manage vehicle acquisitions, sales, financing, insuring, repairs and maintenance. The company's website says it offers a “three-tiered cybersecurity strategy to prevent, protect and respond to cyberattacks.”