HALLOWELL, Maine (AP) — The Maine Public Utilities Commission on Thursday opened an investigation into how earnings decisions drive decision-making by Central Maine Power and its parent, Avangrid.

Commission Chairman Philip L. Bartlett II said CMP has made changes in its management structure, but he noted that its performance is impacted by decisions made by Avangrid.

“While we have seen improvement in CMP’s performance, we want to be sure that it is sustainable,” he said in a statement.

The announcement follows a preliminary probe that followed an audit that was ordered in response to concerns about CMP’s ownership structure.

It wasn’t all bad news for CMP, however.

Regulators lifted a penalty totaling about $12.5 million that had been imposed for billing problems and poor customer service after CMP showed that it had met its performance targets for 18 months.

There are other efforts to ensure CMP’s performance after it was criticized over botched billing system rollout, slow response to storm damage and a controversial utility corridor in western Maine.

This month, Maine Gov. Janet Mills announced she’s introducing a bill to clamp down on electric utility performance with penalties that could include a forced dismantling and sale of assets.

Utilities that consistently miss performance targets could face steep financial penalties, or a utility could ultimately be dismantled and sold if it “consistently fails to meet the requirements.”

Last year, lawmakers voted to replace the state’s privately owned utilities with a consumer-owned utility, but the governor vetoed the bill.