More than 18,450 Maui Electric customers experienced a power outage at 4:03 p.m Thursday.

Areas affected by the power outage included West Maui, Kahului, Haiku, Kihei, Wailea, Hana and Upcountry.

Maui Electric spokesperson Shayna Decker said the outage occurred when a generating unit tripped offline at the Maalaea Power Plant.

She said the cause of the shift offline is under investigation.

Decker said power was restored to a majority of customers by 5:04 p.m.

“Currently, we are waiting for more generation to be available to restore remaining customers,” she said at around 9 p.m. Thursday.

Decker said when the Maalaea generating unit tripped, it caused the electrical frequency on the system to drop suddenly, prompting a “load shed” to various parts of the island to protect the entire electrical system.