Police have arrested ten protesters at the Coalgate mine in Darfield, Canterbury.
About 30 protesters were blocking the entrance to the mine and a further 10 were at the pit of the mine.
Protestors say they want to prevent a planned expansion of the mine, which is currently being considered by Environment Canterbury.
Bathurst Resources' Chief Executive, Richard Tacon, told RNZ reporter, Harry Lock, that their priority has been ensuring the safety of everyone.
