Michigan Gov. Gretchen Whitmer took legal action Friday to shut down a pipeline that carries oil beneath a channel linking two of the Great Lakes.

Whitmer's office notified Canadian company Enbridge that it was revoking an easement granted 67 years ago to extend a roughly 4-mile section of the pipeline through the Straits of Mackinac. The revocation takes effect in 180 days, when the flow of oil must stop.

The decision comes a day after Minnesota regulators approved permits for Enbridge to build a $2.6 billion pipeline across the northern part of the state to replace its aging Line 3.

Whitmer said Enbridge has imposed an "unacceptable risk" of a catastrophic oil spill in the Great Lakes.

"Enbridge has routinely refused to take action to protect our Great Lakes and the millions of Americans who depend on them for clean drinking water and good jobs," the Democratic governor said in a statement. "They have repeatedly violated the terms of the 1953 easement by ignoring structural problems that put our Great Lakes and our families at risk."

Michigan Attorney General Dana Nessel said she filed a lawsuit Friday to carry out Whitmer's decision. Another pending case that Nessel filed last year targets the pipeline as a public nuisance.

Enbridge said there was "no credible basis" for Whitmer's action.

"Line 5 remains safe, as envisioned by the 1953 Easement, and as recently validated by our federal safety regulator," said Vern Yu, the company's president for liquids pipelines.

Line 5 is part of Enbridge's Lakehead network of pipelines that carries oil from western Canada to refineries in the U.S. and Ontario.

Line 5 starts in Superior, Wis., and runs across northwestern Wisconsin and a large swath of Michigan's Upper Peninsula before crossing the Straits of Mackinac into the lower part of the state. The pipeline, which terminates in Sarnia, Ontario, can carry 540,000 barrels per day of oil and natural gas liquids. Propane is made from natural gas liquids, and Line 5 supplies 65% of propane demand in the Upper Peninsula, according to Enbridge.

The underwater section between the Straits of Mackinac, which connects Lake Huron and Lake Michigan, is divided into two pipes that are 20 inches in diameter. Enbridge said they are in good condition and have never leaked. Environmental groups contend they are vulnerable to a catastrophic spill.

Enbridge reached an agreement with then-Gov. Rick Snyder, a Republican, in 2018 to replace the underwater portion with a new pipe that would be housed in a tunnel to be drilled through bedrock beneath the straits.

The company is seeking state and federal permits for the $500 million project, which is not affected by Whitmer's shutdown order.

Environmental activists, American Indian tribes and some elected officials began pushing to decommission Line 5 after another Enbridge pipe spilled at least 843,000 gallons of oil in the Kalamazoo River in southern Michigan in 2010.

Pressure grew as the company reported gaps in protective coating and installed supports when erosion opened wide spaces between sections of pipe and the lake bed.

An anchor dragged by a commercial tug and barge dented both pipes in April 2018. One of the pipeline supports was damaged this summer, apparently by a boat cable.

In a termination notice, Whitmer's office said the easement should not have been granted in 1953. Placing the pipes beneath a busy shipping lane, with no cover to protect from anchor strikes, violated the state's duty to protect the public's interest in Great Lakes waters and bottomlands, the document said.

It referred to a Michigan Technological University report that warned that the straits' swift currents could propel oil over vast distances, potentially damaging fish populations and hundreds of miles of beaches, dunes and wetlands.

The notice said Enbridge repeatedly violated a requirement that the pipelines rest on the lake bed or have other supports at least every 75 feet. Spaces exceeding the threshold have been detected as far back as 1963 and most were never dealt with, it said.

Enbridge has repeatedly defended its operation of the pipeline, saying the coating gaps posed no serious threat. It has installed more than 120 supports to improve stability and stepped up patrols and other measures to prevent anchor strikes.

The company said shutting down Line 5 would cause shortages of crude oil for refineries in Michigan, Ohio, Pennsylvania and eastern Canada, as well as propane shortages in northern Michigan. It also would boost shipments of oil by rail or truck, Enbridge said.

Environmental groups contend there are other means of meeting those demands but that closing Line 5 should be part of a global effort to curb use of climate-warming fossil fuels.

Democratic Sen. Gary Peters, a member of the Senate committee that oversees the U.S. Pipeline and Hazardous Materials Safety Administration, endorsed Whitmer's move and said he would work with officials "to swiftly evaluate alternatives to Line 5 while continuing to hold Enbridge accountable."