Brazilian Indians on Sunday took 100 workers hostage at the construction site of a hydroelectric plant in the southern Amazon region, according to local media reports.
As many as 400 Indians from several different tribes occupied a power plant they say was built on an ancient burial site.
A local administrator says the construction company used dynamite to blow up part of an archaeological site.
Armed with bows and arrows, the Indians occupied the site at dawn on Sunday and confined the construction company's employees to their barracks. There were no reports of injuries.
The Indians are demanding that government officials help negotiate a settlement with the construction company.
The Dardanelos dam on the Aripuana river, some 250 miles north of the Mato Grosso state capital Cuiaba, was due to come online in January 2011, media reports said.