Transportation Secretary Elaine Chao requested Tuesday an audit in a memo to the department’s Inspector General Calvin Scovel. 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 asked Scovel to compile “an objective and detailed factual history of the activities that resulted in the certification of the Boeing 737-MAX 8 aircraft,” according to the memo. Boeing in January 2012 sought an amended “type-certification” for the jet and the FAA issued it in March 2017.

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

“We will fully cooperate in the Department of Transportation’s audit,” Boeing spokesman Charles Bickers said in an email.

The request comes after U.S. federal authorities had already been exploring a criminal investigation of how the 737 Max was certified to fly passengers before the latest crash in Ethiopia, according to people familiar with the probe.

That investigation was prompted by information obtained after a Lion Air 737 Max 8 crashed shortly after takeoff from Jakarta on Oct. 29, said one person, who wasn’t authorized to speak about the investigation and asked not to be named.

The investigation has taken on new urgency after the March 10 crash of an Ethiopian Airlines 737 Max 8 near Addis Ababa that killed 157 people.