Three mushers in Alaska’s Iditarod Trail Sled Dog Race were rescued Friday after they activated their SOS beacons because of deep overflows on the trail. Even before the rescue of 52-year-old Tom Knolmayer, Sean Underwood and Matthew Failor, more than one third of the participants in this year’s 1,000-mile race had quit largely because of conditions. Iditarod officials confirmed the three rescued Friday had officially withdrawn from the race. That brings the number of those who scratched to 23, short of the record of 24 set in 1980. In this year’s race, another musher was removed for not being competitive.