Three men in their 20s were taken to the hospital early Saturday morning with carbon-monoxide poisoning, Nassau County police said.

The men -- ages 20, 21, and 22 -- were asleep inside their recreational vehicle, parked in the Sunrise Mall parking lot in Massapequa when they began to feel ill from carbon-monoxide poisoning about 3 a.m. They are employees of CNY Restoration and Development of Syracuse, police said.

The generator on board was apparently not ventilated properly, causing dangerous fumes to enter the sleeping area, police said.

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Nassau County police ambulance, with the assistance of the Massapequa Fire Department, took all three victims to a hospital for evaluation and treatment.

Injuries are not life-threatening, police said.