The blaze, reported at about 8:20 p.m., began in a second-floor room of the Olympic Motor Lodge, 650 Vanderbilt Motor Pkwy.
The smoker, whose name hasn't been released, admitted to police that he fell asleep while smoking and that when he awoke, his mattress was on fire. When he was unable to extinguish the fire, it spread to two adjoining rooms, police said.
Seven fire departments battled the blaze for more than hour before it was brought under control at about 9:30 p.m. All of the motel guests were safely evacuated, and no one was reported hurt, police and fire officials said.
The smoker has not been charged in the fire, but the Suffolk police department's Arson Squad is investigating. The motel sustained fire and water damage, police said.
Red Cross spokesman Craig Cooper said eight people would be relocated from the motel. All would most likely stay in nearby motels for several days until the Olympic could reopen.
Among those forced from the motel were families who had been originally displaced from their homes by Sandy, Suffolk County police said.
Red Cross spokesman Michael de Vulpillieres said Saturday that none of the eight people the organization helped -- in three rooms: one family of four, a family of three and a person by himself -- were Sandy victims. De Vulpillieres said all had been placed in the motel by the county's Department of Social Services.
Cierra Wynn, 25, of Riverdale, Ga., had been at the hotel for two weeks. She is a dispatching secretary for A-Awesome Towing and Trucking, which is transporting Sandy-damaged cars for an insurance company.
Wynn said she had been sitting in the bar when she noticed people running outside.
"I step out here and see the hotel is up in flames," she said.
Sloat "smelled smoke and then we opened the door and we saw the smoke," Rivera said.
With Olivia Winslow and Candice Ruud