SOUTH PORTLAND — Maine environmental groups are urging South Portland residents to support an ordinance to block tar sands oil from coming to the city.

The Sierra Club and 350 Maine are holding a protest on the Casco Bay Bridge between Portland and South Portland on Saturday.

They’re also calling on the federal government to reject a proposal to transport tar sands from Canada to refineries on in Texas.

The group behind the South Portland ordinance is concerned that a pipeline that currently carries crude oil to Canada would be reversed to send tar sands oil through the city.

But the pipeline company says there is no current proposal to do that. It says that the broadly written ordinance would hurt businesses on the waterfront.