Thousands of Aetna customers across the state, including many in the Sacramento region, were mistakenly sent letters this week telling them that their health care provider is no longer covered in the network and that they need to find new doctors.

More than 8,000 Aetna customers were sent the form letters from the Hartford, Conn.-based health insurance company and have been receiving them in the mail over the past few days.

Since then, patients have been calling their doctors and the insurance company to find out if they are still covered.