The National Transportation Safety Board says a Southwest Airlines plane's nose gear appears to have failed because of "stress overload" when it collapsed during landing at LaGuardia last month, causing the plane to skid and spark down the runway.
The NTSB said in an investigative update statement Tuesday that "no mechanical anomalies or malfunctions have been found."
The gear appears to have failed because of stress overload, the NTSB said. The agency did not elaborate and said no interviews would be given Tuesday.
Sixteen people suffered minor injuries during Flight 345's landing, and passengers had to escape on emergency chutes.
The NTSB also said Tuesday that the first officer, not the captain, was flying the plane on approach into LaGuardia. At some point below 400 feet, there was a change of control and the captain made the landing. It's not clear why.
The NTSB had said already that the plane was at an altitude of about 32 feet, with an airspeed of about 134 knots and a pitch attitude of 2 degrees nose-up about four seconds before landing.
A former senior NTSB investigator told NBC News it's suprising the captain would make such a drastic move unless he had profound safety concerns.
"To try to take command, get established, get the tactile feel for the airplane, and successfully touch the airplane down on the runway is very challenging," said Greg Feith.
The NTSB said the crew was experienced. The first officer had 5,200 flight hours, 1,100 of those in a 737, although this was his first trip in command.
The captain had 12,000 hours of flight time, most in the 737, but this was his first flight with the first officer.
Investigators are still studying the more than 27 hours of recorded data from the entire flight from Nashville, Tenn. to New York, and on Tuesday the agency said it had obtained five videos showing the crash landing that would be analyzed.
-- Andrew Siff contributed to this report.