One of Apple's key manufacturing partners in India has confirmed it was recently the target of a cyberattack that has resulted in confidential Apple documents being leaked on the dark web.

Tata Electronics said on Monday it had detected a "cybersecurity incident," after security researchers told Reuters that ransom group World Leaks had shared more than 200,000 files belonging to Apple and Tesla, both of which are customers of the Indian group.

"A few weeks ago, Tata Electronics identified a cybersecurity incident on some of our systems. Our response protocols were deployed immediately, and the incident has had no impact on our operations across businesses, which remain unaffected," Tata Electronics told Reuters in a statement.

Apple has not commented on the leak, but a source familiar with the matter told the outlet that Apple was investigating the breach and ​a "full analysis was going on." Tata is believed to have received a ransom demand related to the incident, but the group declined to comment.

Many of the leaked files allegedly contain component design and specification papers. For example, one 52-page document has Apple's proprietary markings and purportedly details quality inspection standards ⁠for iPhone circuit ​board components. The files are ⁠also said to contain emails, event logs spanning several years, and passport copies of employees including foreign nationals.

Reuters wasn't able to independently verify the documents, which have been available on the dark web – which is beyond the reach of search engines – since at least June 10, according to researchers.

Tata is emerging as one of Apple's most important manufacturing ​partners outside China, and the breach is another setback for the group. It is also currently facing a health probe over alleged contamination of farmlands near one of its iPhone parts plants.