Medical testing giant Quest Diagnostics discovered “unauthorized access” to its systems on Wednesday, according to an SEC filing Thursday. The company believes attackers accessed patient records but has not disclosed the potential scope of the breach.

The unauthorized access occurred in the company’s Quanum Lab Services Manager, which is used by clients to place orders and check test results. The company is working with law enforcement to investigate the hack according to the 8-K filing , which is mandated by law when a cyberattack occurs.

“While the full scope of unauthorized access remains under investigation, at this time the Company believes that an unauthorized party accessed certain patient records,” the filing explained. “This incident has not materially disrupted the Company’s business operations or its ability to serve patients.”

Quest Diagnostics didn’t immediately respond to questions about how the intrusion was discovered.…