What we know so far is:
1) Yanacocha SA last week stated that no work was taking place at the Conga project.
2) This morning, a committee of anti-mining locals went up to the site, witnessed work taking place and moved in to stop the company activities.
3) This afternoon, some 700 police officers arrived on the scene and displaced the protesters. Tear gas, confrontations, some person to person violence reported.
4) At this moment, the protesters have been corralled into an area by the side of one of the local lagoons.
Hilarity to ensue. Meanwhile, some Peru national media coverage on this link.
UPDATE: Some details and quotes from the anti mine protesters on this link.