(Portland, OR)  --  New details are coming to light regarding an explosion at a bus shelter in Southeast Portland over the weekend.  The Portland Police Bureau says it doesn't appear there were any explosives inside the backpack that was left at the bus shelter off Southeast 122nd Avenue Sunday night.  Police say someone set the backpack on fire, causing some items inside the pack to react with a blast.  No injuries were reported.  Police say they've arrested 43-year-old Russell Brunette on a count of disorderly conduct.