Firefighters were called to the Mariner's Cove Inn about 5:42 a.m. EST to fight a fire that began on west side of the building and the motel was completely in flames by the time first responders arrived, the (Newark, N.J.) Star-Ledger reported.
Authorities said three men were confirmed dead and eight people were hospitalized.
Ocean County Prosecutor Joseph Coronato said 10 people remained missing Friday afternoon.
"We're trying to locate 10 people to make sure they're safe and unharmed," Coronato said.
He said rescuers and investigators are using dogs to search for bodies and possible accelerants in the rubble of the motel.
The cause of the fire was under investigation.