"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," Criswell said.

More than 3,200 residents of Hawaii have registered to receive federal assistance, and that number is expected to rise, Jeremy Greenberg, FEMA's director of response operations, told reporters. FEMA has 300 personnel in Hawaii assisting state and local officials, from search and rescue teams to structural engineers to mortuary service personnel, Greenberg said.

Meanwhile, the search for missing loved ones persisted.

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.

The American Red Cross had received over 2,500 calls from people trying to find and reunite with relatives and friends missing from the fire, said Chris Young, senior director for operations and readiness.

"We've resolved about 800 of the 2,500 so far as we work through it," Young told reporters on Monday. "Communication on the island is still intermittent in many locations."