Hawaii's chief legal officer said on Friday she was opening an investigation into the handling of devastating wildfires that killed at least 80 people in the state this week, as criticism grows of the official response.

The announcement and increased death toll came as residents of Lahaina were allowed back into the town for the first time -- with most finding their homes had been reduced to ashes.

"Everything has been coconut wire," said William Harry, referring to a system of rumours.

"One person heard, then told another, but it's not official information. They don't come here and explain anything."

Another man, who did not want to be named, said he felt he had been left to fend for himself.

"Where is the government? Where are they?" he fumed.

"This is insane. We can't move freely, we don't get the support, now we've heard about looting."

Hawaii's Attorney General Anne Lopez said her office would be examining "critical decision-making and standing policies leading up to, during and after the wildfires on Maui and Hawai'i islands this week."

"My department is committed to understanding the decisions that were made before and during the wildfires and to sharing with the public the results of this review."

Late Friday, Maui county officials gave an updated death toll from the disaster.

"The number of fatalities is at 80," the county said, adding that 1,418 people were at emergency evacuation shelters.

The number of people killed surpassed the count from when a tsunami struck the Big Island in 1960.

"Without a doubt, there will be more fatalities. We don't know ultimately how many will have occurred," Governor Josh Green said.

Firefighters were continuing to extinguish flare-ups and contain wildfires in Lahaina.

Maui County Police Chief John Pelletier said on Thursday that as many as 1,000 people could be unaccounted for, though he stressed that this did not mean they were missing or dead.

The fires follow other extreme weather events in North America this summer, with record-breaking wildfires still burning across Canada and a major heat wave baking the US southwest.

Europe and parts of Asia have also endured soaring temperatures, with major fires and floods wreaking havoc. (AFP)