(CNN) — Boeing has not turned over important records to investigators probing the door plug blowout on a 737 Max earlier this year, investigators say. That, Boeing signaled Wednesday afternoon, is because there are no records.

The records in question are documentation of steps on the assembly line last fall when National Transportation Safety Board investigators believe Boeing employees removed critical bolts that hold the plug in place, but did not reinstall the bolts before the plane left the Boeing factory in October 2023. The plane flew about 150 commercial flights before the door plug flew off the plane mid-flight on January 5, just over two months ago.

“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,” National Transportation Safety Board chairwoman Jennifer Homendy said Wednesday in testimony before the US Senate Commerce Committee.

She testified that because of Boeing’s actions, NTSB investigators do not know who on the Boeing assembly line removed and reinstalled the door plug that — months later while the plane was in service carrying passengers — blew out.

After her testimony, Boeing followed up with a statement: “With respect to documentation, if the door plug removal was undocumented there would be no documentation to share. We will continue to cooperate fully and transparently with the NTSB’s investigation.”

The Federal Aviation Administration has recently identified issues with processes on Boeing’s manufacturing line. Earlier this week, it said a six-week audit of the company identified “non-compliance issues in Boeing’s manufacturing process control, parts handling and storage, and product control,” although it did not specify the specific shortcomings.

NTSB investigators have made multiple visits to Boeing facilities and created a special team to handle requesting and processing documents from Boeing and its key contractor, Spirit AeroSystems. Boeing said it has “worked proactively and transparently to fully support the NTSB’s investigation.”

“Our team works tirelessly with the NTSB team to respond comprehensively to all NTSB information requests and bring information to them that would be relevant to their investigation,” Boeing said.

In particular, Homendy said, investigators are keen on identifying the actual Boeing employees who had their hands on the door plug bolts.

“There is one team – one team – that deals with the doors,” Homendy said. The team includes 25 employees and a manager, and she called it “absurd” and “really disappointing” that NTSB still did not have names.

Following her testimony, Boeing signaled that it was providing the requested list of names.

“Early in the investigation, we provided the NTSB with names of Boeing employees, including door specialists, who we believed would have relevant information,” Boeing said. “We have now provided the full list of individuals on the 737 door team, in response to a recent request.”

A source familiar with the request said the specific ask for those names was submitted to Boeing over the last weekend.

Homendy also raised concerns with Spirit’s approach to the probe, saying three individuals Spirit presented to the NTSB for interviews actually did not work for the company, and instead worked for a subcontractor. Spirit has not commented on Homendy’s comments.

Homendy said the FAA has been “very cooperative” with the NTSB probe.

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