MACKINAW CITY, Mich. (AP) — Officials say crews have finished capping and sealing two electric cables that were severed by a suspected boat anchor strike in the waterway that connects Lake Huron and Lake Michigan.

A team of investigators led by the U.S. Coast Guard said Monday the cables owned by American Transmission Co. were returned to the bottom of the Straits of Mackinac.

The company is working with the Michigan Department of Environmental Quality on a plan to remove them.

Officials said they’re still investigating what caused the damage, although the state attorney general says a tugboat anchor was dragged across them April 1.

About 600 gallons of mineral oil insulation fluid leaked from the cables, while roughly 625 gallons were recovered.

Also damaged were two oil pipelines and another company’s out-of-service electric cables.