By David Shepardson

WASHINGTON (Reuters) -The Nationwide Transportation Security Board is conducting a brand new spherical of interviews with Boeing (NYSE:) and Federal Aviation Administration personnel this week in its probe of the January Alaska Airways 737 MAX 9 in-flight emergency.

NTSB Chair Jennifer Homendy on Wednesday stated investigators had been again on the 737 plant in Renton, Washington, this week for extra interviews.

“We’re taking a look at different cases the place a door plug was opened and closed to ensure that these information can be found,” Homendy stated at a U.S. Senate listening to, saying investigators need to be sure that these different cases had been documented.

Boeing, whose shares fell 2% on Wednesday, declined to touch upon the interviews.

Final month, Boeing stated it believed that required paperwork detailing the removing of the door plug within the Alaska Airways airplane concerned within the emergency had been by no means created.

Homendy stated on Wednesday that Boeing and investigators nonetheless have no idea the personnel who labored on the Alaska Boeing 737 MAX 9 that suffered the emergency. “This work occurred in September. They transfer numerous planes by way of that manufacturing facility,” Homendy stated. “The most important concern is lacking information.”

At problem is the method not the people, she stated. “This is not a gotcha on anyone,” Homendy stated, including the NTSB has nonetheless been unable to interview the door plug staff supervisor, who has been on sick go away.

The door plug panel blew off the Alaska Airways flight not lengthy after the airplane took off from Portland, Oregon, on Jan. 5.

Homendy stated investigators are additionally wanting on the planemaker’s security tradition. She stated the NTSB might conduct a security tradition survey at Boeing.

Homendy stated the planemaker was working nicely with the NTSB and offering paperwork sought. Boeing needs to know what went flawed: “They need to know they usually need to repair it,” Homendy stated.

Following the incident, the FAA grounded the MAX 9 for a number of weeks, barred Boeing from rising MAX manufacturing, and ordered the corporate to handle systemic quality-control points inside 90 days after an audit discovered fault with the corporate’s manufacturing processes.

The NTSB stated beforehand that 4 key bolts had been lacking from the door plug that blew out.

The Justice Division has opened a felony investigation into the emergency.

Homendy in March criticized what she referred to as Boeing’s lack of cooperation and failure to reveal some paperwork, together with on the door plug opening and shutting, in addition to the names of 25 staff on the door crew in Renton. After Homendy’s feedback, Boeing supplied the 25 names, and the planemaker stated it was cooperating.

The NTSB plans to carry a public investigative listening to into the Alaska Airways incident on Aug. 6-7.

Homendy stated the listening to would come with testimony from staff at Boeing and fuselage producer Spirit AeroSystems (NYSE:) and others like Alaska Airways.