More than two-thirds of Oahu had power restored as of noon today, 18 hours after a blackout left the entire island without electricity, forced the Honolulu airport to cancel flights, closed shopping malls and left motorists crawling through streets with no lights.

Hawaiian Electric Co. has restored power to 229,000 of its 293,000 O'ahu customers as of noon today, spokeswoman Lynne Unemori said.

HECO is still investigating the cause of the outage and have tentatively scheduled a press conference for 2:30 p.m. today at its Ward Avenue offices, across from the Neal Blaisdell Center.

Jan Loose, HECO spokeswoman, said power is being brought back up neighborhood by neighborhood so as not to overload the grid.

Major areas in Honolulu's primary urban core were back online as well as many communities in Central and Leeward Oahu, Pai said.

"Service has been restored to the airport and all of the major hospitals as well," Pai said.

He was not able to provide an estimate on how quickly service to the remaining customers will be restored.

The utility company has not been able to pinpoint where the problem started.

"Four of our major transmission lines tripped offline, three of them coming out of the Kahe power plant and one out of Waiau," Pai said.

He estimated that it will take "many more hours" for some of those without power to have it restored.

"We are asking those customer's whose power has been restored to please practice conservation to ensure stability on the (electricity distribution) grid," Pai said.