Quest Diagnostic Inc. has been hit by a data breach, in which an unauthorized user accessed data from nearly 11.9 million patients.

The data included financial information, Social Security numbers and medical information, but not laboratory results, Quest said in a June 3 press release. The information was collected by a Quest contractor that provides billing collections services called the American Medical Collection Agency.

Quest was initially notified of unauthorized activity on May 14 and on May 31, AMCA said the breach included documents from millions of patients.

Collections requests to AMCA have since been suspended. Quest said AMCA has not yet provided full details of the incident, including who may have been impacted, but patients will be notified in compliance with the law.