The company that operates twin oil pipelines in a Great Lakes waterway says it knew three years ago that protective coating had been damaged but didn't inform regulatory agencies.

Enbridge Inc. says a gap was opened in enamel coating on one section of Line 5 in Michigan's Straits of Mackinac as a support anchor was being installed in 2014. The coating gap is one of several that have exposed bare metal on parts of the pipelines.

Company spokesman Ryan Duffy says the gaps are being repaired and haven't compromised the pipelines' safety.

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But state officials are criticizing Enbridge's failure to disclose the damage earlier.

Michigan Agency for Energy Director Valerie Brader says her office's trust in Enbridge "has been seriously eroded."

The Straits of Mackinac links Lakes Huron and Michigan.