An Ontario judge has ordered Algonquin protesters to vacate a property where Frontenac Ventures wants to explore for uranium.

Judge Gordon Thomson granted the injunction Monday, giving the mining company "immediate, unfettered and unobstructed access" to the land blockaded by the Ardoch and Shabot Obaadjiwan Algonquin First Nations since June 29.

The injunction also gives police the authority to remove people camped on the property near Sharbot Lake, about 60 kilometres north of Kingston.

Ardoch First Nation co-chief Paula Sherman says the ruling came as a shock since only last week the judge ruled the protesters could stay and only their camp buildings had to go.

"It really seems to be a kind of about-face," Sherman told CBC News. "You know, over the weekend, something must have happened to change his mind. We're kind of flabbergasted actually."

Although the relationship between protesters and the Ontario Provincial Police has been peaceful up to now, Sherman says that could easily change.

"If we're invaded and the OPP tries to come in here, there's going to be confrontation," she said.

"We're urging Dalton McGuinty to get involved here before something escalates out of control."

The First Nations are opposed to uranium mining, saying the environmental impact could contaminate the land and the water.

Frontenac Ventures was not available for comment.