Firefighters are trying to determine the cause of a duplex fire in Coralville Wednesday evening. The fire started at 6 p.m. at 710 and 712 4th Avenue Place in Coralville. Firefighters were able to contain the fire to the attic and roof area of both units in about 30 minutes. But there is smoke and water damage to both of the units. No one was injured. The Red Cross is helping the three people that lived inside who are now displaced. Firefighters stayed at the scene until 8:30 p.m. The fire caused about $50,000 in damage.