Thousands of car dealerships across the United States have seen their operations crippled for a second day in row on Thursday.
The cause was a cyberattack on software provider CDK Global, which offers a range of programmes to manage customer data, process sales and book appointments.
CDK Global shut down its systems for several hours on Wednesday after the initial incident. But after a restart, another cyberattack followed.
The company is now trying to make the software available again as quickly as possible, said a spokeswoman.
The nature of the attack remained unclear as of Thursday.
US media said dealers had received a message from the company saying it could be several days before the issues are resolved. In the meantime, some car sellers had resorted to old-fashioned pen and paper methods.
The company said it has around 15,000 car dealers as customers.
A company statement said in full: "Late in the evening of June 19, we experienced an additional cyber incident and proactively shut down most of our systems. In partnership with third party experts, we are assessing the impact and providing regular updates to our customers. We remain vigilant in our efforts to reinstate our services and get our dealers back to business as usual as quickly as possible."