Lansing Police are still looking for Bill Lynn Brann, who was last seen Thursday afternoon in Fenner Nature Center.
Brann, 65, is also known to frequent Hawk Island Park.
Police have been conducting searches in the area with helicopters and ATVs.
Volunteer groups are joining in the search on Sunday, as part of a training exercise.
Please call Lansing Police at 483-4600 if you have any information on Brann's whereabouts.