The National Transportation Safety Board has not received documents from Boeing crucial to its investigation of the emergency door blowout, board chair Jennifer Homendy said on Wednesday during a Senate committee hearing.

Why it matters: Two months after the incident, safety investigators still have not determined who is responsible or how it occurred, as the company's safety culture is reportedly unstable.

• "Boeing has not provided us with the documents and information that we have requested numerous times over the past few months, specifically with respect to opening, closing and removal of the door and the team that does that work at the Renton facility," Homendy said.
• The NTSB's attorney is involved with the situation, she said.

The latest: Boeing said it has worked proactively to support the NTSB's investigation in a Wednesday statement following the hearing.

• "Early in the investigation, we provided the NTSB with names of Boeing employees, including door specialists, who we believed would have relevant information," the statement said.
• "We have now provided the full list of individuals on the 737 door team, in response to a recent request. With respect to documentation, if the door plug removal was undocumented there would be no documentation to share."

State of play: A team of 25 people and a manager is responsible for work on these door plugs in the Renton facility, located in Washington.

• The NTSB has not received the names of these employees or information from the company about the day that work was done on this door plug.
• The team's manager has been out on medical leave and unavailable for an interview with investigators, Homendy said.

Investigators have been on site at the Renton Facility since Sunday conducting interviews, which are expected to continue through the rest of the week.

• The board has been told that Boeing has a procedure to document when door plugs are removed, but investigators have not been able to verify this, per Homendy.
• "Either they exist and we don't have them or they do not exist," she said.

What's next: Sen. Ted Cruz (R-Texas) asked Homendy to inform the Senate committee in writing by March 13 whether Boeing has cooperated with the board's requests.

• "This investigation needs to get to the bottom of what occurred and what caused that accident," he said.

Go deeper: Review finds "disconnect" between Boeing management and staff on safety