Scientists may have discovered in Minnesota what could be the oldest human artifacts ever found in North America: stone tools dated 13,000 to 15,000 years ago.

"Archaeologists in the northern Minnesota town of Walker dug up the items, which appear to be beveled scrapers, choppers, a crude knife and several flakes that could have been used for cutting," said Colleen Wells, field director for the Leech Lake Heritage Sites Program.

"They don't look like much,'' Wells acknowledged. "They don't look pretty.''

The findings triggered a lot of skepticism but also great interest. The archaeological team found around 50 objects in 2006 while investigating a route for a planned road.

The objects were situated beneath a layer of glacial deposits that had been covered by windblown deposits. "The finding is intriguing but it really needs to have its precise age nailed down and more needs to be known of the artifacts,'' said David Meltzer, an archaeologist at Southern Methodist University in Dallas. "Much more research needs to be done to allow firm conclusions," said Wells.

It must also be assessed whether the items are really human-made artifacts or merely rocks that were chipped by glaciers during the Ice Age or if they were left at the site by humans, or carried there by glaciers or water.

"Other researchers have found that that part of Minnesota apparently was something of an "oasis'' around 13,000 years ago, an area free of ice cover with shifting glaciers on most sides but with an access route to the southeast," said Matt Mattson, one of the archaeologists.

Many scientists believe that people existed in Minnesota that long ago. "It seems to be there is an increasing body of science that there were stone stools and people here in that time period in North America,'' said Dan Rogers, chairman of the anthropology department at the National Museum of Natural History at the Smithsonian Institution in Washington.

The main theory says people first entered the Western Hemisphere 11,200 years ago, via a land bridge from Asia over what is now the Bering Strait (the Clovis culture). Now it is increasingly believed that people arrived earlier in the Americas, and that Indians were not the first race to have occupied the continents.

The archaeologists hope to preserve the site for sometime in the future when a more advanced testing technique might be available. "We're looking at absolutely irreplaceable links in human history here. Once it's gone there's no retrieving it'', said Mattson.