(Portland, OR)  --  One person is dead, after a tractor-trailer rig crashed into rail cars parked off Highway 30 near the St. Johns Bridge.  The driver of the rig, which was carrying fuel, was killed when the semi exploded into flames around nine o'clock yesterday morning.  The train cars were carrying liquid asphalt, and also caught fire, sending a large column of black smoke into the air.  Firefighters brought the flames under control in about two hours.  No one else was injured.