Hawaiian Electric Co. officials say the unexpected shutdown Wednesday of Oahu’s largest generator affected 57,000 residential and business customers and prompted the utility to launch emergency outages across the island.

The 180-megawatt generator at Campbell Industrial Park shut down around 11:23 a.m., leading to outages in Waialua, Kahuku, Waihee, Kaneohe, the Kapiolani area, downtown Honolulu, Waiakamilo, Moanalua, Halawa, Moanalua and Waipahu, HECO officials said. The plant is operated by the independent power producer AES.

Power to most affected customers was restored shortly before noon, HECO spokesman Darren Pai said.

“The targeted emergency outages were necessary to avoid a more widespread outage or damage to the electric system from an imbalance of too much demand versus too little available generation,” HECO said. Company officials said they would be working with AES to investigate the cause of the plant shutdown.

City officials first announced the outages late Wednesday morning.

Hawaiian Telcom also experienced problems Wednesday with its TV, Internet and voice-over Internet protocol services.

Spokeswoman Ann Nishida said about 800 businesses and residential customers were affected, primarily on Oahu, and that the problems started about 10:30 a.m. and lasted just more than an hour.

“The root cause is still under investigation,” Nishida said.