Investigators have more clues about the plane crash that killed Paul and Sheila Wellstone, and six other people. But the cause of the crash is still a mystery. Some investigators are already heading back to Washington with information they collected at the crash site. But they say they won't have any answers for a long time.

	NTSB investigators are combing through the wreckage of the plane which crashed in Eveleth Friday. They expect to remain on the scene for at least a few more days. See more images. (Photo by Jiim Mone, Associated Press)

A county road winds through the forest behind the Eveleth airport. The Wellstones' plane went down not far from the road. On Sunday morning, two SUVs came speeding down the road away from the crash site. Each truck pulled a trailer covered with a blue, plastic tarp. Battered hunks of airplane propeller were poking out from under the tarps. They were on their way to a hangar at the airport where investigators could get a closer look.

A few minutes later, a big chartered bus with tinted windows came rolling up the road going in the other direction -- toward the crash site. The bus carried 17 people who are related to the victims of the crash. The family members spent about half an hour at the site of the crash.

The plane went down in a thick stand of pine and spruce trees. Most of the big pieces of debris had been removed when the relatives arrived, but there was still part of a wing, and bit of the plane's tail. The ground was covered with a blanket of ashes.

	Relatives of the plane crash victims were taken in this bus to the crash site on Sunday. (MPR Photo/Chris Julin)

Officers from the St. Louis County sheriff's department had hauled in a load of hay bales. When the relatives left, the bales were covered with evergreen branches. The mound of greenery was dotted with red roses. Someone left a photograph of Paul Wellstone and his aid, Will McLaughlin, who also died in the crash. Someone left a bird's feather.

Investigators say they don't know what caused the plane to plunge into the ground 2.5 miles from the airport. The National Transportation Safety Board is leading the investigation, and Carol Carmody is the acting chair of the NTSB. She met with reporters on Sunday in Eveleth.

"The investigation has gotten to a very difficult stage for our people. We're at the hand-sifting of debris to try to pick out aircraft parts or instrument parts. We're using small brushes to dust pieces off. We're using sifters. It's a very meticulous, slow-going process," she said.

Carmody says they've found a few pieces of the cockpit and a couple of gauges from the instrument panel. But much of the plane was reduced to ashes during fire after the crash.

	Mary McEvoy, 49, was a professor of educational psychology at the University of Minnesota's Twin Cities campus. McEvoy was married and had three teenage children. She was the deputy chair of the DFL Party in Minnesota.

Carmody says she's still puzzled by the course the plane took just before it crashed. The investigators have pieced this much together from the radar records: The pilot radioed ahead for clearance to land in Eveleth. The plane was approaching the airport. Then, in the last few minutes the plane was in the air, it slowed down and started to turn away from the airport. Carol Carmody says the plane was pointed away from the runway when it crashed.

"We find the whole turn curious. And we're going to have to look carefully at the speeds we've calculated and the distances," she said.

Carmody says the pilot did not radio in to say he was having problems during those last few minutes. She says the investigators are looking at lots of possibilities. The plane could have iced up. Other pilots reported icing that day, but not severe icing. Instruments could have failed - on the plane or at the airport. There are lots of other possibilities.

Carmody says investigators will wrap up their work at the crash site in a matter of days. But she says it will be months before they announce any conclusions.