AUGUSTA — Maine regulators on Thursday rejected a proposal from a Canadian company to buy one of the most important utilities in the state.

Enmax of Calgary, Alberta, wants to buy Emera Maine from its Nova Scotia-based parent company for about $1 billion.

Emera has more than 150,000 customers and serves the northern and eastern parts of Maine.

But the Maine Public Utilities Commission voted 2 to 1 against the proposal. The commission cited risks to ratepayers, one of which was whether the purchase would make system upgrades less likely, the Bangor Daily News reported.

One of the commissioners also raised a concern about Enmax’s plan to fund most of the acquisition by debt.

The two utilities announced the sale about a year ago. Both companies said they still plan to go ahead with the sale and keep working with the commission. Commissioners said the plan could be accepted with changes.