New Hampshire fire officials have identified three people who died of carbon monoxide poisoning after a malfunction in a propane-fired furnace. Fire Marshal J. William Degnan said the investigation into the deaths in Plaistow continues. Four people were discovered in a house about 11:30 a.m. Tuesday when firefighters were asked to check on them. Three people died. They were identified Thursday as Kirk Walsh, 32; Maryanne Comparato, 47; and John Adams Jr., 28. A fourth victim was taken to Massachusetts General Hospital. His name and condition were not released.