(The Hill) — The Federal Aviation Administration (FAA) is expanding its probe into Boeing that began in the wake of a midair blowout on a 737 Max 9 aircraft earlier this month.

“After taking decisive action to ground 171 Boeing 737-9 MAX airplanes, the FAA is now investigating Boeing’s manufacturing practices and production lines, including those involving subcontractor Spirit AeroSystems, bolstering its oversight of Boeing, and examining potential system change,” the agency said in a statement Wednesday.

An “explosive decompression” occurred Jan. 5 on the Alaska Airlines flight from Portland, Ore., to Ontario, Calif. when a panel plugging an unused emergency exit door blew off midflight.

Last week, the FAA started an investigation into whether Boeing failed to ensure its planes complied with the agency’s safety regulations.

The FAA also announced that it is increasing the oversight of Boeing’s production last week, including auditing its production.

In its announcement, the FAA said it is conducting “an audit involving the Boeing 737-9 MAX production line and its suppliers to evaluate Boeing’s compliance with its approved quality procedures.”

FAA Administrator Mike Whitaker said the “grounding of the 737-9 and the multiple production-related issues identified in recent years require us to look at every option to reduce risk.”

“The FAA is exploring the use of an independent third party to oversee Boeing’s inspections and its quality system,” Whitaker said in the release.

Dave Calhoun, Boeing’s CEO, has said his company will “cooperate fully and transparently” with the FAA and National Transportation Safety Board investigations.

“We’re going to approach this, No. 1, acknowledging our mistake with 100 percent and complete transparency every step of the way,” Calhoun said, addressing his employees.