HALLOWELL, Maine (AP) The Maine Public Utilities Commission is opening an inquiry into the preparedness and response of Maine’s electric companies following a powerful windstorm the day before Halloween.

The storm left more than half the state’s population in the dark, and it took Central Maine Power up to 10 days to restore power to all customers.

All told, about 400,000 CMP customers and 90,000 Emera Maine customers lost service, making it the largest power outage in Maine history.

The Portland Press Herald reports that the PUC on Tuesday asked Central Maine Power and Emera Maine to file a report detailing their responses and lessons learned in 30 days.

The PUC isn’t the only entity looking into the storm response. The public advocate’s office and state lawmakers also are planning their own inquiries.