The five told rescuers that they have survived on food and water on the bottom level of what had been the three-story grocery store.
Sixteen members of the team are cutting through concrete blocks to reach five, who have been speaking with the rescuers.
The team of 80 specialists are on a search-and-rescue mission through the wrecked mass of concrete and metal in Haiti's earthquake-ravaged capital, using technology that has been improved since the Sept. 11 attacks.
The squad touched down in Port-au-Prince on Saturday after a two-day wait for clearance to land at the destroyed city's overloaded airport.
Deputy police inspector Robert Lukach, who serves in the New York Police Department's elite Emergency Services Unit, said he's more optimistic about finding survivors in Haiti than he was at ground zero.
"That quickly became a recovery mission. But this is still a rescue mission, and we are hoping for the best," he said.
He said that even days after the quake, he is hopeful there are pockets in the rubble where people may still be alive, although the crew was worried they would arrive too late, after too much waiting around.
The team, which plans to spend at least a week in Haiti, is one of 28 federal urban search and rescue teams around the United States that can mobilize during a disaster.
They are bringing three tractor-trailers full of equipment, including sound gear to listen for survivors trapped below wreckage, cutting tools that can smash through concrete and shore up rubble as they burrow down, and rescue dogs.