TRAVERSE CITY, Mich. (AP) — Environmental activists and some members of Congress are concerned about two oil pipelines beneath a waterway linking Lakes Michigan and Huron.

The pipes owned by Enbridge Energy Partners cross the bottom of the Straits of Mackinac in northern Michigan, a popular resort area. They're part of a line that carries oil between North Dakota and several Upper Midwestern states.

The lines were laid in 1953. The company says they've never leaked and are safe.

But critics fear they could rupture the same way another of Enbridge's lines did in 2010, spilling 843,000 gallons of crude into the Kalamazoo River in southwestern Michigan.

Enbridge has signed an agreement with Michigan Technological University to conduct sonar inspections of the lines with an underwater robot.