State Capitol police hastily evacuated the Capitol at 5:15 p.m. on Monday as a precaution after state officials learned that a small, stolen plane might be headed toward Madison.

Federal officials told the Wisconsin Air National Guard at about 3:30 p.m. that a suspicious Cessna 172 had entered Wisconsin air space and the pilot was not responding to messages from the Federal Aviation Administration. Two of the Guard’s F-16 fighters jets took off at about 5 p.m. to try to make contact with the plane, which the North American Aerospace Defense Command in Colorado said was believed stolen from Thunder Bay, Ontario, at 2:30 p.m. by a student pilot.

NORAD spokesman Mike Kucharek said the Cessna 172 was south of Madison at about 5:30 p.m. and had been heading southwest. He said the plane had been flying erratically but was not believed to be a terrorist threat.

Brig. Gen. Don Dunbar, Wisconsin’s homeland security adviser, ordered an evacuation of the Capitol at about 5 p.m. as a precaution, according to the Air National Guard.

During the evacuation, Capitol police urged bystanders to walk at least one building away. Many workers had already left for the day, and Gov. Jim Doyle was in Chicago on Monday. Police cars with sirens on drove on the sidewalks by the doors of the Capitol. Others drove on the streets of the Capitol Square, telling people to move away.

The evacuation order was lifted at 5:44 p.m.

Kucharek said that by 7:15 p.m., the Cessna 172 had traveled south over Illinois and was approaching the St. Louis area with the pilot continuing to refuse to communicate with authorities.

"We don’t know what the motive is. I wouldn’t want to speculate on that. We are treating this with the most utmost seriousness," Kucharek said.

Plans were being made to swap the Wisconsin jets out for other aircraft as the pursuit continued, Kucharek said.

The pilot had acknowledged seeing the F-16s but he had not obeyed their nonverbal commands to follow them, Kucharek said in a telephone interview from Colorado Springs.

"They have got his attention. Now it is a flight safety issue. That is why we are tracking him," Kucharek said.

The plane had enough fuel to fly for nearly eight hours, but it was unknown how much training the student pilot has, Kucharek said. The Web site cessna.com indicated the Cessna 172 Skyhawk is a four-seater with a range of about 790 miles and top speed of 141 mph.