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Drugstore chain Walgreens said on Sunday it would end its relationship with Theranos, in another blow for the blood-testing company that was once lauded for its innovative approach but has increasingly come under scrutiny.

Walgreens said it would shutter all 40 Theranos Wellness Centers at its stores in Arizona, having already stopped Theranos laboratory testing services at its location in Palo Alto, California.

The latest announcement meant Walgreens would no longer offer Theranos services at any of its stores.

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"In light of the voiding of a number of test results, and as the Centers for Medicare and Medicaid Services (CMS) has rejected Theranos' plan of correction and considers sanctions, we have carefully considered our relationship with Theranos and believe it is in our customers' best interests to terminate our partnership," Brad Fluegel, Walgreens senior vice president and chief health care commercial market development officer said in a statement.

In a statement, a Theranos spokesperson said the company is working closely with government officials to ensure it not only complies with all federal regulations but exceeds them.

"We are disappointed that Walgreens has chosen to terminate our relationship and remain fully committed to our mission to provide patients access to affordable health information and look forward to continuing to serve customers in Arizona and California through our retail locations," the spokesperson said.

Theranos was once praised for its fast, less-invasive blood testing technology but the company has found itself in the spotlight after media reports raised questions about the accuracy of its proprietary tests.

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Federal prosecutors from the U.S. Attorney's office and the SEC have investigated Theranos over whether it misled investors, the Wall Street Journal reported in April.

Theranos also faced allegations that most of its tests were in fact performed with traditional lab machines, not its proprietary Edison device, prompting potential sanctions against the company's CEO, Elizabeth Holmes. The WSJ reported in May that Theranos had voided all results for Edison-device tests conducted in 2014 and 2015.