CHICAGO (AP) — Medical laboratory operator Quest Diagnostics said it learned of a cyber breach of one of its systems this week, likely compromising some records for patients.

In a Thursday regulatory filing, Quest Diagnostics reported “unauthorized access” to its Quanum Lab Services Manager, a platform where certain clients can place test orders and receive or look up their results. The company said it discovered the hack on Wednesday and notified federal law enforcement.

How many patients and which particular records have been affected is still unknown. Quest Diagnostics said it believes “certain patient records” were accessed in the breach, but that the full scope remains under investigation.

The New Jersey-based company said it's also working with external cybersecurity experts to assist in its response.

Quest Diagnostics has seen hacks impacting patient records before. In 2016, for example, the company said data including lab results and contact information of about 34,000 people was exposed in another online breach. And in 2019, other personal information belonging to about 11.9 million Quest patients was affected after a separate hack at American Medical Collection Agency, a billing collections service provider.

Cyberattacks are on the rise across industries. Beyond healthcare, other breaches have recently disrupted anything from supermarket chains to core education applications.

Governments and companies worldwide are working more broadly on online security updates. Urgency erupted this week, after an AI-assisted discovery of vulnerabilities in a programming language called PHP, which is vital to 70% of websites globally.

Outages and limited service have continued for many as firms rush to patch those risks. But based on the company's investigation, Quest Diagnostics confirmed to The Associated Press Thursday that its cyber breach was not related to the PHP issue.