ORLANDO, Fla. — Millions of patients of Quest Diagnostics medical lab may be impacted by a data breach at a billing collections agency connected to the company.

• American Medical Collection Agency had data breached
• Quest Diagnostics, other companies contract with AMCA
• Not known what other companies may be affected

Quest announced Monday that an unauthorized user gained access to the data at American Medical Collection Agency, which works with several medical companies, between August 2018 and March 2019, according to a filing by Quest Diagnostics to the U.S. Securities and Exchange Commission.

The SEC document says the information accessed includes credit card numbers and bank account information, medical information, and other personal information.

Quest says that, according to AMCA, 11.9 million Quest patients may have been affected.

AMCA notified Quest that the unauthorized user also had access to other information from other medical companies, but it's not known which ones.

The SEC document shows Quest suspended sending collection requests to AMCA and is working to verify the accuracy of the information.

Quest is also working to notify patients as well.