Interior Minister Carlos Romero says the miners have placed large rocks in the roads, forcing hundreds of cars to stop.
Heavily armed riot police are on hand but have not moved against the protesters.
The miners are demanding control of the lucrative Colquiri mine, which is 100 miles (160 kilometers) south of La Paz. The mine has been a point of dispute between them and a group working for a state-owned company.
On Monday, the other group set off small dynamite charges in the roads to demand control of the mine.