(Portland, OR)  --  An investigation is under way into threats of violence at a middle school in Milwaukie.  Police say students at Rowe Middle School spoke up Saturday after seeing the threatening posts in a gaming chat room.  Police say officers visited the home of the student accused of making the threats and determined there was no immediate threat to the school.  School officials say they'll have a police presence on campus through the end of the school year out of "an abundance of caution."