(Salem, OR)  --  Oregon's top federal prosecutor is taking an indefinite leave of absence.  U.S. Attorney Amanda Marshall told "The Oregonian" she's unable to serve at this time because of health issues she's had for months.  Marshall was confirmed as U.S. attorney by the U.S. Senate in 2011 after she was nominated by President Obama.  First Assistant U.S. Attorney Billy J. Williams is taking over for Marshall on an interim basis.