ST. PAUL — Minnesota regulators on Thursday approved Enbridge Energy’s proposal to replace its aging Line 3 oil pipeline across the northern part of the state, even though a major, controversial question remains unresolved: the line’s route.

All five members of the Public Utilities Commission backed the project, though some cited heavy trepidation. In open discussion before the vote, several cited the deteriorating condition of the existing line, which was built in the 1960s, as a major factor.

“It’s irrefutable that that pipeline is an accident waiting to happen,” Commissioner Dan Lipschultz said ahead of the vote. “It feels like a gun to our head … All I can say is the gun is real and it’s loaded.”

“I think it’s clear where we’re all going,” Commissioner John Tuma said. “It’s just a matter of working out the details.”

Some pipeline opponents reacted angrily when it became clear earlier Thursday how the vote would go. Tania Aubid, a member of the Mille Lacs Band of Ojibwe, stood and shouted, “You have just declared war on the Ojibwe!” Brent Murcia, of the group Youth Climate Intervenors, added: “We will not let this stand.”

Tribal and climate change activists have teamed up to fight the project, arguing in part that the pipeline risks spills in pristine areas in northern Minnesota where Native Americans harvest wild rice. Ojibwe Indians, or Anishinaabe, consider wild rice sacred and central to their culture.

Several commissioners said the issue posed a difficult decision. Chairwoman Nancy Lange choked up and took off her glasses to wipe her eyes as she described her reasoning. Another commissioner, Katie Sieben, said it was “so tough because there is no good outcome.”

Commissioners did not discuss the route during morning deliberations. The current pipeline crosses two Native American reservations whose tribes strongly oppose the project.

Enbridge has proposed a route that bypasses those reservations, but the tribes and climate change activists oppose that route, too. The company says it needs to replace the pipeline because it’s increasingly subject to corrosion and cracking.

The pipeline currently runs from Alberta, Canada, across North Dakota and Minnesota to Enbridge’s terminal in Superior, Wisconsin. Enbridge has said it would continue to run Line 3 if Minnesota regulators rejected its proposal, despite its accelerating maintenance needs.

Much of the discussion at the Line 3 hearings over the past several days has focused on whether Minnesota and Midwest refineries need the extra oil. Enbridge currently runs Line 3 at about half its original capacity of 760,000 barrels per day for safety reasons, and currently uses it only to carry light crude.

The project’s opponents, including the Minnesota Department of Commerce, argue that the refineries don’t need it because demand for oil and petroleum products will fall in the coming years as people switch to electric cars and renewable energy sources. Opposition groups also argue that much of the additional oil would eventually flow from to overseas buyers.

Enbridge and its customers strongly dispute the lack of need in the region. They said Line 3’s reduced capacity is already forcing the company to severely ration space on its pipeline network, and that failure to restore its capacity would force oil shippers to rely more on trains and trucks, which are more expensive and less safe. Business and labor groups support the proposal for the jobs and economic stimulus.