Five people were killed Sunday in an early morning blaze that engulfed an entire house in suburban Atlanta, authorities said. The cause of the fire had not yet been determined, a Gwinnett County fire department spokesman said in a statement, though investigators said they were "unable to rule out" a backyard fire pit as the potential culprit. Firefighters were called to the scene in an unincorporated section of Gwinnett County at 3:30 a.m. Sunday after neighbors reported seeing smoke and flames coming from the two-story home, the statement said.