Indianapolis fire investigators are searching for the cause of a house fire Sunday that injured a mother, her son and a firefighter. Nellie Spears, 67, and her son, Lonnie Groce, 43, were injured in the fire in the 600 block of Holly Avenue. Spears, the homeowner, was taken to Wishard Hospital for smoke inhalation and was in fair condition Sunday night. Groce suffered serious burns to his arms and was in critical condition. The injured firefighter was treated at Methodist Hospital and released.