AUBURN - Bob Bartone couldn't believe the two chips of stone fit together, like pieces of a puzzle.

The first was pulled from the ground west of the Auburn-Lewiston Municipal Airport in December. The pointed brown stone, an inch long, was obviously part of an ancient tool, possibly used to clean animal skins between 9,000 and 11,000 years ago.

It was enough to bring a full archaeological excavation to Auburn, part of a joint effort by the University of Maine at Farmington's Archeological Research Center, the airport and the Maine Historical Preservation Commission.

Last week, members of the airport digging team found another piece of stone tool. Bartone, assistant director at the research center, was skeptical that it would match the first.

"We found the first half almost six months ago, and it was streaked differently," he said.

But sure enough, UMF graduate Jake Grindle - the dig assistant - lined them up. It was the biggest find so far at the excavation.

Bartone and his team will be on hand through the rest of the month, removing a ton of soil from the land west of the airport's longest runway, looking for more stone tools, stone chips and bits of charcoal from an ancient hearth, a fire pit that's been cool for at least 9,000 years.

"If we're lucky enough, we'll find one of those," he said. "That would give us so many different kinds of information about how the site was used and where the people came from."

Bartone figures the site dates to years immediately following the most recent ice age, between 9,000 B.C. and 7,000 B.C. The area would have been uninhabitable until the glaciers retreated, leaving behind a wide-open tundra that would be populated by animals and people hunting them.

The entire area, from Moose Brook north to the Little Androscoggin River, has been known to archaeologists for years. Bartone said there are at least six dig sites that turned up paleo-Indian artifacts in the square mile surrounding the Auburn airport. The Maine Historic Preservation Commission lists more than 5,500 such camp sites across the state.

Bartone and his team are trying to learn more about those first Mainers.

"The artifacts and their context, their relation to each other across the site and down through the ground is really what helps us piece things together," he said. "You can show me some stone tools and chips at the lab, and it's very interesting. But if I know those things were found in some relationship to each other, it tells me a lot more."

A dig on the southern portion of the airport a decade ago turned up typical artifacts - stone tools and the chips left over from making and sharpening them.

Bartone said he thinks the newer site, on the northern part of the airport, is connected to the site just south of it. It's located just above a small basin and was miraculously left untouched by airport development.

Until now.

Airport Manager Rick Cloutier said a new taxiway will go through the site. State construction permits required an archaeological survey because artifacts had been found in the area. Bartone and a group from UMF last fall found paleo-Indian artifacts, enough to ask for a full excavation.

Cloutier said the dig works well with the rest of the taxiway project. Bartone and his team expect to finish their work this month and the taxiway construction should begin in July.

"They really worked well to get this rolling," Cloutier said. "They made a commitment to come in and get it done in time for us to move ahead."