The U.S. Department of Transportation has asked for a wide-ranging review of how the government and Boeing Co. certified the 737 Max — the jet that’s been involved in two fatal accidents since October.

Transportation Secretary Elaine Chao requested the audit in a memo to the department’s Inspector General Calvin Scovel, according to a press release Tuesday. The new audit is separate from the criminal probe that the Inspector General is also conducting in conjunction with the Department of Justice’s Criminal Division.

Chao’s move opens a new front in the U.S. government’s inquiries into the Oct. 31 crash of an Indonesian 737 Max and another crash of the same model in Ethiopia on March 10. The 737 Max family of jets was grounded by the Federal Aviation Administration on Wednesday after evidence surfaced linking the two crashes.

A Boeing representative wasn’t immediately available for comment.

–With assistance from Richard Clough.

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Photo Credit: U.S. secretary of transportation Elaine Chao speaking at an event in 2018. Fortune Brainstorm / flickr