Activists blocked the gates to an Enbridge plant Tuesday morning to protest a controversial tar sands pipeline project.

The action targets the company's plan to reverse the flow of its Line 9 pipeline from North Westover, Ont., to Montreal, allowing the eastward flow of crude from the Alberta tar sands and U.S. Bakken shale.

According to reporting by the Montreal Gazette, three protesters locked themselves to the refinery's gates, while a fourth scaled a tripod.  The small citizen group was ultimately arrested and charged with mischief.

Explaining why they took the direct action, Alyssa Symons-Bélanger, one of the four activists at the scene, said in a press statement: "We want to send a clear message to the oil companies and to the Harper and Couillard governments: the residents of Quebec are opposed to the transportation of the tar sands and are calling for an immediate halt to their extraction."

Canada's National Energy Board gave approval to the reversal in March this year, prompting rebuke from environmental groups in Canada and the U.S.

Supporters of the action took to Twitter to mark the action as it unfolded:

#actionligne9 Tweets