TUCSON, Ariz. (AP) _ The search for a missing Air Force attack jet resumed today on a snow-covered Colorado mountain near the spot where radar last tracked the aircraft.

Two Cessna 182 planes were searching and more aircraft were expected to join the effort to find the A-10 Thunderbolt II attack jet that left Davis-Monthan Air Force Base in Tucson last Wednesday morning.

The search was focused on the 12,467-foot New York Mountain, about 20 miles southwest of Vail, Colo.

``We know he went off the radar there but there's a possibility of a 5-mile grid path. He could have glided in (any direction) up to a 5-mile radius, so that's where we're looking,'' said Lt. Cindy Butler of the Colorado Civil Air Patrol.

The pilot, Capt. Craig Button, had been training about six weeks to fly the A-10, an $8.8 million plane that carried four 500-pound bombs and a 30mm Gatling gun.

When the jet is found, the investigation will focus on why Button flew to Colorado _ 775 miles off the path to the Barry M. Goldwater bombing range. After the jet vanished, Federal Aviation Administration records showed, radar intermittently tracked an unidentified plane traveling in the opposite direction of the targeted bombing range.

The Pentagon was investigating Button's background, including the time he was stationed at Laughlin Air Force Base in Del Rio, Texas, the CBS ``Evening News'' reported Monday. The report said that when Button had training flights at Laughlin, he had requested they be routed through Colorado.

The Air Force today continued to dismiss speculation that the plane, nicknamed Warthog, was sabotaged or stolen.

``We have no physical evidence that supports any of the theories that are out there,'' said Capt. Mike Richmond, a Davis-Monthan spokesman. ``All we have at this point is factual indicators in the form of eyewitness accounts and radar imagery.''

New FAA information showed a possible radar track between Vail and Eagle, Colo. A motorist along Interstate 70 reported seeing smoke on the New York Mountain one day last week. Other visual sightings had a low-flying plane making two wide, opposing circles before disappearing.

Capt. Andrew White, another spokesman of Davis-Monthan base, said it appears the aircraft made some course adjustments that an autopilot couldn't make.

Last week, officials said the pilot could have become incapacitated and may have activated the plane's autopilot mechanism. He also could have ejected, though no parachute was seen by his colleagues over Arizona.