(Plymouth, WA)  --  A fire that raged following an explosion at a liquefied natural gas plant Benton County, Washington is now extinguished.  Plymouth residents who were ordered to evacuate their homes following Monday's blast were allowed to return yesterday.  Plant officials say the gas that's still leaking from a tank at the facility is not toxic and chances are slim that another explosion will take place.  Five people were injured in the explosion, and four of them have been released from the hospital.