MONTPELIER, Vt. — Environmental groups in Maine and Vermont are raising an alarm about the potential for tar sands oil to be piped across northern New England.

The groups say energy companies are eyeing an existing oil pipeline that carries oil from Portland to Montreal with the idea of reversing the flow and sending Canadian tar sands through Portland.

They’re planning news conferences for 11 a.m. today in Portland and 11 a.m. in Montpelier to air their concerns.

A plan to move Canadian tar sands oil through a pipeline extending through the Great Plains to the Gulf Coast has generated heated national debate.