As the death toll in Hawaii from the deadliest U.S. wildfire in more than a century grew to 99 on Monday, Hawaii Gov. Josh Green said there is a grim expectation of further casualties. 

"There are more fatalities that will come," Green told CBS News. "The fire was so hot that what we find is the tragic finding that you would imagine, as though a fire has come through and it's hard to recognize anybody."

All residents of Lahaina — a historic town that bore the brunt of the blaze — have either escaped or perished in the fire, according to Green, but it could take 10 days for a full death toll to be determined as crews could find "10 to 20 people per day probably until they finish " 

"We are prepared for many tragic stories," Green said.

Lahaina has proven difficult for rescuers to access. Green has surveyed the town's ruins twice, and said the magnitude of the destruction has left the area unrecognizable. 

"There's nothing to see except full devastation. The buildings are almost non-existent," he said.

Hawaii has a statewide outdoor warning siren system, which can be used to notify residents ahead of natural disasters or human-caused events, including tsunamis, hurricanes, dam breaches, flooding, wildfires, volcanic eruptions, terrorist threats and hazardous material incidents, according to the Hawaii Emergency Management Agency.  

But U.S. Rep. Jill Tokuda, whose district includes Maui, said Sunday on "Face the Nation" that the warning sirens "likely did not go off," suggesting the Lahaina fire was too fast-moving.

The issue of emergency alerts and why sirens weren't activated is something Green said will be investigated by the state's attorney general. The investigation, Green said, aims "not to find fault in anyone but to say why this worked and this didn't work." 

Despite the failure of alarms, Green said that given the fire's intensity and the weather conditions on Maui when the wildfires ignited, crews had limited options to slow the blaze. 

"if you put a fire truck in the way of the flames that were coming through at 1,000 miles an hour, the fire truck would have been incinerated, in addition to the people," he said. "So it's unlikely that much could have been done except of course moving people out before, and that's what we'll talk about."