LUDINGTON, Mich. (AP) — A coal-powered passenger steamship on Lake Michigan that’s the last of its kind in the U.S. will stop using coal to fuel its historic engines once its operators settle on an alternate power source.

Lake Michigan Carferry Inc. is early in its search for what could replace the coal that currently propels the S.S. Badger on treks between Ludington, Michigan, and Manitowoc, Wisconsin.

The company’s general manager, Sara Spore, tells that company officials are “looking at all of our options” and there’s no timeline yet for when a power conversion might happen.

The ship can accommodate 600 passengers and 180 vehicles. It operates between May and October.