AUGUSTA — The Maine Public Utilities Commission says there’s no need for a formal investigation into a rate increase imposed by the ferry line that serves the Casco Bay islands.

Island residents went to the commission after the Casco Bay Transit District increased rates last May, raising average passenger fares between 95 cents and $1.05 during peak season and between 35 cents and 45 cents in the off season.

The commission today concluded that the rate increase was justified. Casco Bay’s revenues by law must be adequate to meet its ongoing obligations.