Bossier City fire investigators are looking into the cause of a Tuesday afternoon house fire in the 1000 block of Traffic Street.  Heavy smoke and flames were coming from the single-story wood frame house when firefighters arrived.  A man and two youg boys, aged 2 and 4, were in the house at the time of the fire but they got out safely.  The fire is believed to have started in a bedroom but its exact cause is not yet known