LYNN – Two Lynn firefighters were hospitalized Wednesday for carbon monoxide poisoning they suffered after an emergency back-up power generator malfunctioned inside Fire Department Headquarters, according to District Fire Chief James Barry.The two firefighters suffered “serious, but non life-threatening injuries,” Barry said.One man was taken to Mass. General Hospital and the other was brought to Lynn Union Hospital.A third firefighter was also in the building when the carbon monoxide leaked but he did not require medical attention.Barry declined to identify the victims but said both men have been working for the fire department for about 15 years.The situation unfolded at about 2:35 p.m., Barry said, when Lynn firefighters were returning from a call in Saugus where they mutually aided in putting out a small blaze at Spuds Restaurant on Lincoln Avenue.As Ladder 2 was returning to fire headquarters at 725 Western Ave. firefighters noticed clouds coming from the roof and thought there might be a small fire near the roof of the building.There was no fire, but in the meantime the two firefighters started to become disoriented and lethargic, Barry said.Barry said preliminary indications show the carbon monoxide came from a back-up power generator, but says full details of the situation are still being investigated.”The situation is currently being investigated by the Inspectional Services Department,” he said.The building was ventilated and completely operational on Wednesday, Barry said.