(Seaside, OR)  --  An investigation is ongoing into a fire that destroyed two homes in Seaside.  Firefighters responded to the houses located on 4th Avenue early yesterday morning.  At least five propane tanks exploded during the fire, causing some damage to a home across the street.  Highway 101 was closed while the fire was put out.  The highway has reopened.  No one was hurt in the fire.  Firefighters from six nearby departments responded to help.  The cause of the fire is under investigation.