LAS VEGAS, Nev. (AP) _ Passengers who had just boarded a Detroit-bound Northwest Airlines jet Monday evacuated when the cabin reportedly began to fill with smoke.

However, a Northwest spokesman said there was no smoke and that the 140 passengers evacuated after one passenger, believing he smelled smoke, opened an emergency exit.

Steve Herman, an Associated Press reporter on the plane at McCarran International Airport, said no evacuation order was given but that the passengers filed in an orderly manner out the front of the plane after the exit was opened.

Herman said the pilot said there was a problem with smoke in the cabin but did not tell passengers to evacuate.

Northwest spokesman Red Tyler in Minneapolis said the escape exit had to be put back together before passengers could reboard the plane.