WASHINGTON (AP) -- Federal investigators say the plane that crashed near Teterboro Airport last month may have been too nose-heavy to take off.
The National Transportation Safety Board updated its investigation of the Feb. 2 crash in which a jet shot off the runway and across busy Route 46 before crashing into a warehouse.
No one was killed, but 20 people were injured in the accident, including the driver of one of two cars hit by the plane.
In the update, the NTSB said the plane's weight distribution may have contributed to the crash. Investigators found the jet's center of gravity ''to be well forward of the allowable limit,'' though they haven't said why.
When that happens, the plane won't take off, said Denny Lassard, chairman of Safety Science Department at Embry-Riddle Aeronautical University in Prescott, Ariz.
The plane contained full or nearly full fuel tanks, a passenger load at or near capacity, and few pieces of luggage when it crashed. Those factors and the plane's cabin configuration all affect how its weight is distributed, the report said.
Pilot John Kimberling told investigators in the days after the crash that when he tried to lift the nose of the aircraft, the controls appeared to jam and the plane would not respond, forcing him to make a split-second decision to abort takeoff.
Investigators made their updated assessment after weighing contents recovered from the wrecked plane and viewing video recordings obtained from the Port Authority of New York and New Jersey.
The report also ruled out icing as a possible cause of the accident.
Safety board spokesman Keith Holloway said the agency is continuing to look at several factors that may have caused the crash.
The autopilot and pitch control systems will continue to be studied, according to the report.
It often takes more than a year before the NTSB makes a final determination of the cause of a plane crash.
There has been serious fallout from the crash. Earlier this month, the Federal Aviation Administration grounded Platinum Jet Management, the company that hired the flight crew. The agency said the Fort Lauderdale, Fla., company may be unqualified to fly passengers and that it had failed to comply fully with FAA requests for documents.
On Wednesday, the FAA also grounded Darby Aviation, known as AlphaJet, saying that it improperly allowed Platinum Jet to handle the flight. AlphaJet, based in Muscle Shoals, Ala., maintains the action is ''completely unfounded, and we're going to challenge it,'' said its lawyer, Mark McDermott.
The FAA also has approved a $500,000 grant to study safety improvements at Teterboro Airport, a busy airport for corporate jets taking passengers to and from New York.
"This was as sloppy an operation as we've seen in a long time," said NTSB chairman Mark Rosenker.
Nearly 300 U.S. commercial airports lack 1,000-foot end-of-runway margin that the government considers adequate for safety.
A $500,000 federal grant will be used to make safety improvements to an airport runway.