Bird remains found in both engines of the US Airways jetliner that ditched into New York's Hudson River last month have been identified as Canada geese, federal safety officials said Thursday.

The National Transportation Safety Board said experts at the Smithsonian Institution who examined 25 samples of bird remains made the determination.

They have been unable to determine how many birds were involved in the crash, in which all 155 crew members and passengers survived.

Canada geese typically range in size from about 6 pounds to 12 pounds. The safety board said the type of engines on the ditched airliner, an Airbus A320, are designed to withstand a collision with a bird weighing up to 4 pounds without catching fire or causing damage severe enough to release of engine fragments outside the engine case. The engines also are supposed to still be able to be shut down by the pilot.

However, federal aviation regulations do not require the engines to be able to continue to generate thrust after sucking in a bird 4 pounds or larger.

Flight 1549 reported moments after taking off from New York's LaGuardia Airport on Jan. 15 that the airliner had lost thrust in both engines after striking birds. Pilot Chesley "Sully" Sullenberger told investigators he glided the plane to a landing in the river rather than risk a catastrophic crash in a densely populated area.

The accident has focused attention on the problem of airplanes colliding with birds. Canada geese have been a particular concern because they are larger than most other birds and because their populations are growing.

The high speeds at which commercial airliners fly greatly magnifies the force of an impact, and the larger the bird, the greater the impact.

From 1990 to 2007, there were nearly 80,000 reported incidents of birds striking nonmilitary aircraft, about one strike for every 10,000 flights, according to the Federal Aviation Administration and the Agriculture Department.

Those numbers are based on voluntary reports, which aviation safety experts say almost certainly underestimate the size of the problem and fail to convey the severity of some incidents.