(Polk Co., IA) -- Police in three states are on the lookout for an elderly man who went missing in central Iowa. The Polk County Sheriff's Office says 81-year-old Mitchell Riley and his wife stopped at a rest area in northern Polk County early Wednesday morning while driving from Minnesota to Missouri. The sheriff's office says Riley lost track of his wife and left the rest area without her driving a U'Haul truck with Arizona license plates. The sheriff's office says Riley's wife checked several exits along Interstate-35 in Ankeny but he still hasn't been found. Riley suffers from Alzheimer's and doesn't have his medication. Anyone with information is asked to call the Polk County Sheriff's Office (515)286-3333.