(Lewiston, MN)  —  The investigation into a Rush Creek fish kill is continuing.  State pollutions inspectors are talking to landowners in the surrounding area to determine whether toxic runoff cause the massive die-off of brown trout last month near Lewiston.  The incident was the area’s third major fish kill in recent years.  Investigators say finding an exact cause is difficult because pollution flows quickly downstream.  More than 25-hundred fish were found dead July 25th, and investigators believe the die-off was most likely caused by contaminated runoff after heavy rains.