KETCHUM, Idaho (KLIX) Authorities are warning drivers to be cautious as they head north towards Galena Summit as a rock fall has blocked part of the highway. The Blaine County Sheriffs office says Highway 75 has been reduced to one lane. Drivers are being told to drive with "extreme caution" between Titus Creek Road and Galena Summit. The lane blockage is roughly 22 miles north of Ketchum.