Jaguar Land Rover (JLR) has warned that it believes “some data” has been accessed in a cyber attack which caused the car maker to halt production.
JLR had previously said there was “no evidence” data had been stolen.
The company said on Wednesday that its investigations have now indicated that some data has been impacted and it will inform regulators.
It will contact anyone whose data has been affected by the hack, the company said.
The firm, which is owned by India’s Tata Motors, shut down its systems on August 31 after becoming aware of issues affecting its global operations.
Production is still paused at its factories in Halewood on Merseyside and Solihull in the West Midlands, as well as at its engine manufacturing site in Wolverhampton.
Factory workers are currently on standby and being informed on a daily basis over whether or not return to their sites.
An English-speaking hacker who calls himself “Rey” has claimed responsibility for the hack.
A spokesman for JLR said: “Since we became aware of the cyber incident, we have been working around the clock, alongside third-party cybersecurity specialists, to restart our global applications in a controlled and safe manner.
“As a result of our ongoing investigation, we now believe that some data has been affected and we are informing the relevant regulators.
“Our forensic investigation continues at pace and we will contact anyone as appropriate if we find that their data has been impacted.
“We are very sorry for the continued disruption this incident is causing and we will continue to update as the investigation progresses.”