Power authorities are still investigating the cause of a power outage that affected more than 22,000 homes in the Western Bay of Plenty early Monday.

Powerco network operations manager Phil Marsh said the power cut happened about 1.20am on Monday and affected 22,439 customers in Omokoroa, Bethlehem, Katikati and surrounding areas.

Supply was fully restored to properties by about 2am and Powerco is still investigating the cause of the outage.