The death toll of the Maui wildfires has risen to 99 with hundreds still missing and dozens more feared dead as search crews go street by street through burned-down neighbourhoods.

The blazes that consumed most of the historic town of Lahaina, are already the deadliest in the United States in more than a century, with the death toll having stayed at 96 for almost two days.

Hawaii's Governor Josh Green had earlier said crews "will find 10 to 20 people per day, probably, until they finish. And it's probably going to take 10 days. It's impossible to guess, really".

Twenty cadaver dogs and dozens of searchers are making their way through blocks reduced to ash.

"They're going street by street, block by block between cars, and soon they'll start to enter buildings," Jeff Hickman, director of public affairs for the Hawaii Department of Defense, said on NBC's Today.

At a White House briefing on Monday, Federal Emergency Management Agency (FEMA) administrator Deanne Criswell said more cadaver dogs were on their way to Lahaina, but that the search was "extremely hazardous" and would take time.

"There are structures that are partially standing that engineers have to clear first to make sure it's safe for the search-and-rescue teams to go into," Ms Criswell said.

As mobile phone service was slowly restored, the number of people missing dropped to about 1,300 from more than 2,000, Mr Green added.

A crowd-sourced database circulating on social media showed about 1,130 individuals listed as "not located" on a list of about 5,200 people as of Monday afternoon.

The database includes names collected from "missing persons" notices posted at shelters as well as information submitted by loved ones.

Mr Green had said on Sunday that 500 hotel rooms will be made available for locals who have been displaced.

An additional 500 rooms will be set aside for workers from FEMA which has also started to provide $US700 ($1080) to displaced residents to cover the cost of food, water, first aid and medical supplies, Ms Criswell said.

The money is in addition to whatever amount residents qualify for to cover the loss of homes and personal property.

"We're not taking anything off the table, and we're going to be very creative in how we use our authorities to help build communities and help people find a place to stay for the longer term," Ms Criswell said.

The Biden administration is seeking $US12 billion in additional money for the government's disaster relief fund as part of its supplemental funding request to Congress.

The blaze that swept into centuries-old Lahaina nearly a week ago destroyed nearly every building in the town of 13,000.

That fire has been 85 per cent contained, according to the county. Another blaze known as the "Upcountry" fire has been 60 per cent contained, officials said.

"There's very little left there," Mr Green said of Lahaina in a video update Sunday, adding that "an estimated value of $5.6 billion has gone away".

Even where the fire has retreated, authorities have warned that toxic by-products may remain, including in drinking water, after the flames spewed poisonous fumes.

Many people have gathered at the War Memorial Gymnasium in Wailuku, which has been serving as a shelter.

Among the visitors was Oprah Winfrey, a part-time Maui resident, who told Hawaii News Now that she has delivered personal hygiene products, towels and water in recent days.

She warned that news crews will eventually depart from the destruction, and the world will move on. But said that "we're all still going to be here trying to figure out what is the best way to rebuild … I will be here for the long haul, doing what I can".