GitHub is investigating a breach of its internal repositories after the TeamPCP hacker group claimed to have accessed approximately 4,000 repositories containing private code.

GitHub's cloud-based development platform is used by more than 4 million organizations (including 90% of the Fortune 100) and over 180 million developers who contribute to more than 420 million code repositories.

The company has yet to share more information about the investigation, but said it currently has no evidence that customer data stored outside its internal repositories has been affected.

"We are investigating unauthorized access to GitHub's internal repositories," GitHub told BleepingComputer when asked for further details.

"While we currently have no evidence of impact to customer information stored outside of GitHub's internal repositories (such as our customers' enterprises, organizations, and repositories), we are closely monitoring our infrastructure for follow-on activity."