Local, state and federal law enforcement agencies are working together on the investigation of a fatal apartment fire Saturday morning. One person was killed and another suffered critical injuries at the Executive Apartments in Beaver Dam. Four other residents were taken to a hospital for treatment of fire-related injuries. No names have been released yet. The weekend’s fatal fire came just one month after a man was killed while apparently working with explosives in another Beaver Dam apartment. Authorities are still trying to determine the cause of the latest fire.