A man in his 60s was found dead inside his Nashua home after a two-alarm blaze at the residence Wednesday, the Fire Department said. The man, who was not identified, was discovered inside the 2½-story, wood-frame home on Carlisle Road, Deputy Fire Chief Michael O’Brien said. The fire was reported by neighbors at 2:07 p.m. after they heard an explosion at the home, O’Brien said. He said the fire was quickly extinguished after firefighters arrived. The state fire marshal is investigating the cause of the blaze, O’Brien said.