With telephones down on Abaco and Grand Bahama islands, residents posted lists of missing loved ones across social media.
A single Facebook post by media outlet Our News Bahamas seeking the names of missing people had 1,600 comments listing lost family members since it went live on Tuesday morning.
Dorian packed sustained winds of 110 miles per hour (175 kph) and was moving northwest at 6 mph (9 kph), as it churned about 95 miles (155 km) east of Cape Canaveral, Florida, the NHC said in an 11 p.m. EDT (0300 GMT) advisory.
Forecasters said that one or two tornadoes were possible overnight on the Florida coast, and that risk would later shift to Georgia and South Carolina.
Hurricane-force winds had expanded to 60 miles (96 km) from the storm's core. "Dorian is expected to remain a powerful hurricane during the next couple of days," the NHC said.
The exact toll in the Bahamas will not be clear until the storm completely passes and rescue crews can get to devastated areas, said Theo Neilly, the Bahamian consul general in Washington.
"We expect it to be very devastating and the damage to be extreme," Neilly said. Dorian has battered the Bahamas for the past three days.
As many as 13,000 homes in the Bahamas may have been destroyed or severely damaged, the International Federation of Red Cross and Red Crescent Societies said, in the strongest storm ever to hit the Bahamas.
Food may be required for 14,500 people in the northern Bahamas' Abaco Islands and for 45,700 people in Grand Bahama, the U.N. World Food Programme said in a statement. The preliminary estimates were based on an assessment by representatives of Caribbean nations, the WFP and other groups.
The U.S. Agency for International Development said on Twitter it was airlifting critical relief items, such as plastic sheeting, hygiene kits, and water containers, from Miami to the Bahamas. The U.S. Coast Guard said four of its helicopters were assisting in humanitarian efforts.
Dorian, which killed one person in Puerto Rico before striking the Bahamas on Sunday, is tied for the second-strongest Atlantic storm to make landfall with Gilbert (1988), Wilma (2005) and the 1935 Labor Day hurricane.
It was expected to hit Florida with hurricane conditions overnight, before bringing its powerful winds and dangerous surf along the coasts of Georgia, South Carolina and North Carolina by late on Thursday.
The governors of those states have ordered evacuations of coastal counties.
President Donald Trump declared a state of emergency for South Carolina on Tuesday, freeing funds, other federal resources and manpower to assist during the storm and aftermath recovery.
Emergencies have already been declared in Florida and Georgia.
