POCATELLO, Idaho (AP) — The exact location of the Bear River Massacre in eastern Idaho has been determined, an archaeologist says.

State Historic Preservation Office Director Ken Reid said he and a team from Utah State University used modern technology and maps created by soldiers at the 1863 massacre that left up to 500 Northwestern Shoshone dead.

The Idaho State Journal reports that Reid presented his findings Saturday to the Pocatello Historic Preservation Committee at Idaho State University.

"I suspect it turned into a traffic jam and then a slaughter," Reid said about how women and children fled along the bottom of a ravine during crossfire from soldiers on both sides.

The commanding Army officer involved counted 220-270 dead. Settlers who went in later found many more bodies in ravines or under deep snow and put the number as high as 500, a figure cited in a National Park Service history. The tribe estimates 400 of their number were killed. No more than 60 survived.

Darren Perry, vice chairman of the Northwest Band of the Shoshone Nation, said many tribal members already knew the location.

"We were the tribe that was massacred in 1863," Perry said at the meeting. "My grandmother showed me where the lodges were, and her grandfather showed her."

Perry said his great-grandfather was a 12-year-old survivor and eyewitness.

Tribal members each year in late January gather in the area to offer songs and prayers to the dead.

Reid said the Bear River has shifted several times and that the confluence with what is now named Battle Creek was about 750 yards north at the time of the massacre. He said soldier maps and modern technology helped determine the previous river channel. Reid said the massacre site is in Franklin County near Preston. It's within a 718-acre area designated by the National Park Service in 1990.

Reid said the task of identifying the site was made difficult because a railroad settlement occupied the ravine from 1878 to 1886. In the 1890s an irrigation diversion canal was built across the site. Then in 1911 a blowout of the Winder Reservoir destroyed or buried much of the camp area.

Reid said all that activity means artifacts are mingled.

Experts say fire heaths in the area created by native people date back more than 1,000 years, and the ravine along Battle Creek is believed to have been a winter gathering place for centuries.