Maine utility regulators are investigating fare increases recently put in place by Casco Bay Lines.

The ferry service says the increases are necessary as it faces a multi-million dollar deficit.

According to the Portland Press Herald, some islanders say the rate hikes disproportionately impact infrequent ferry customers, including seniors over 65 who don’t commute daily between the islands and mainland Portland.

The Maine Public Utilities Commission says it investigating and said claims by ratepayers about irregularities in the rate-setting process are credible.