SAN FRANCISCO (CBS SF) – The personal information of millions of Quest Diagnostics lab patients may have fallen into the hands of hackers.

The massive data breach impacts nearly 12 million patients.

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Quest is one of the biggest blood testing providers in the country. The company has are dozens of locations across the Bay Area.

The data includes patients’ credit card and bank account numbers, Social Security numbers and medical information, but not test results.

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A billing vendor, American Medical Collection Agency told Quest that an ‘unauthorized user’ gained access to the system.

Quest told CBS it has stopped using AMCA and is alerting patients.

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Meantime, patients who have used the lab’s services should contact Quest Diagnostics immediately to find out if their data was impacted.