Mop up work continues today on the brush fire on the south side of Interstate 84 Exit 87 at the east end of The Dalles that generated a large and quick response by firefighters on Thursday before being brought under control.  Helicopter drops helped bring the fire under control after it started in the mid-morning hours near the railroad tracks south of the freeway.  Mid-Columbia Fire and Rescue Chief Bob Palmer estimated the fire to be eight-to-nine acres in size, but there were a number of factors that made it difficult to deal with, including a strong wind, the fire being in a bit of draw between the freeway and the railroad tracks, and spotting.  Palmer noted there was some spotting of the fire along the hillside, but crews were able to catch them quickly and prevent spread.  He added the big concern was the fire spotting into the Columbia View Heights area, but firefighters were able to prevent that from happening.  Palmer said the investigation into what caused the fire is continuing.