WASHINGTON, March 6 (Reuters) - The head of the National

Transportation Safety Board said on Wednesday that Boeing ( BA )

has not provided some documents and information sought in

its ongoing investigation into the Jan. 5 Alaska Airlines 737

MAX 9 mid-air cabin door emergency.

NTSB Chair Jennifer Homendy said investigators have sought

the names of the 25 people who work on door plugs at a Boeing ( BA )

facility in Renton, Washington, but have not received them from

Boeing ( BA ). "It is absurd that two months later we don't have it,"

Homendy said at a Senate Commerce hearing.

"It's not for lack of trying," she said, adding that the

information being sought includes the precise shift that worked

on the improperly installed door plug in September. The agency

also seeks documentation related to opening and closing of the

door plug and removal of key bolts.

Boeing ( BA ) did not immediately comment.

The NTSB said last month four key bolts attaching the plug

to the fuselage appeared to be missing.

The planemaker has scrambled to explain and strengthen

safety procedures since the January mid-air incident that led to

the FAA grounding the MAX 9 for several weeks. The company has

been the subject of increased scrutiny from regulators and big

air carriers concerned about the quality of jet production.

Homendy said investigators began interviews at Boeing's ( BA )

Renton plant on Sunday and that they will continue all week.

Senator Ted Cruz, the top Republican on the Commerce

Committee, called it "utterly unacceptable" that the NTSB is not

receiving full cooperation from Boeing ( BA ).

Senate Commerce Committee Chair Maria Cantwell said she

planned to write a letter asking about the lack of cooperation.

Boeing's ( BA ) CEO, Dave Calhoun, told employees in January:

"We're going to approach it with 100% and complete transparency

every step of the way. We are going to work with the NTSB who is

investigating the accident itself to find out what the cause

is."