WASHINGTON (Reuters) -The head of the Federal Aviation Administration said Thursday the agency was "too hands off" in oversight of Boeing ( BA ) before a January mid-air emergency in a new Alaska Airlines 737 MAX 9, as it pursued multiple investigations into the planemaker.

FAA Administrator Mike Whitaker's comments at a Senate Commerce Committee hearing mark the first time the U.S. aviation regulator has acknowledged inadequate oversight in the Jan. 5 incident, in which a door panel blew out during the flight.

"The FAA should have had much better visibility into what was happening at Boeing ( BA ) before Jan. 5," Whitaker said.

He said the agency had permanently boosted the use of in-person inspectors and that he would visit a Boeing ( BA ) factory in South Carolina on Friday.

The FAA's approach before the mid-air incident "was too hands off, too focused on paperwork audits and not focused enough on inspections," Whitaker added.

"We will utilize the full extent of our enforcement authority to ensure Boeing ( BA ) is held accountable for any noncompliance. We currently have multiple active investigations into Boeing ( BA ) and are processing a number of reports filed by whistle-blowers."

Whitaker in February barred Boeing ( BA ) from boosting production of its best-selling plane. He said last month he did not expect Boeing ( BA ) to win approval to increase production of the MAX "in the next few months."

Whitaker also said the agency will continue increased on-site presence at Boeing ( BA ) and its supplier Spirit AeroSystems "for the foreseeable future."

He added there must be a "fundamental shift" in Boeing's ( BA ) safety culture.

"We have been too much in reactive mode, waiting for some event to occur and analyzing the event to find out what to do differently. So we're shifting to a much more proactive approach. On the manufacturing side, it's introducing inspectors and coming up with clear indices to monitor performance," Whitaker said.

Whitaker said the FAA has "additional inspections at critical points of the production process."

On May 30, Boeing ( BA ) delivered a comprehensive quality improvement plan to the FAA after Whitaker in late February gave Boeing ( BA ) 90 days to develop a comprehensive plan to address "systemic quality-control issues."

The National Transportation Safety Board said earlier the door panel that flew off a Boeing 737 MAX 9 jet mid-flight was missing four key bolts and no paperwork exists for the removal of those bolts. Whitaker confirmed no paperwork exists.

The Justice Department has opened a criminal probe into the MAX 9 incident.