WASHINGTON (Reuters) -The National Transportation Safety Board (NTSB) is investigating United Airlines Boeing737 MAX 8 flight last month that experienced "stuck" rudder pedals during the landing rollout, the agency said on Thursday.

The NTSB said in a preliminary report on the Feb. 6 flight that the plane taxied to the gate at Newark Airport without incident and there were no injuries to the 161 passengers and crew.

It reported that the captain said that during the landing rollout, the rudder pedals did not move in response to "normal" application of foot pressure while attempting to maintain the runway centerline.

Boeing ( BA ), the Federal Aviation Administration and United did not immediately respond to requests for comment.

Boeing ( BA ) has been under scrutiny in recent months after a Jan. 5 mid-air blowout on another plane model, a Boeing 737 MAX 9. Last month, the FAA formally mandated inspections in Boeing 737 MAX airplanes for loose bolts in the rudder control systems after the planemaker recommended them in December.

The NTSB report said the captain said that in the MAX 8 flight last month the pedals remained "stuck" in their neutral position and the captain used the nosewheel steering tiller to keep the airplane near the runway centerline while slowing to a safe speed before exiting the runway onto a high-speed turn-off.

The NTSB said the captain asked the first officer to check his rudder pedals and the first officer reported the same problem. The captain said that shortly thereafter the rudder pedals began to operate normally.

Three days after the incident, United conducted a test flight and was able to duplicate the reported rudder system malfunction identified during the incident on the same plane.

The NTSB was notified of the flight control issue after the flight test result and opened an incident investigation.