Frank William Brunel, 52, was last seen around January 1, 1994, in Clearlake Oaks, California. He wasn’t reported missing until 2013, and the circumstances of his disappearance remain unclear.

Brunel worked with blue-green algae (cyanobacteria) in Northern California and Oregon. He was 5 feet 10 inches, about 165 pounds, with blond hair, blue eyes, and a distinctive burn scar on the right side of his face. Reports say he was owed a substantial sum of money, and there are suspicions that foul play may have been involved.

Despite investigations, the case is unsolved and authorities continue to seek information. Can anyone who knew Brunel or his work with cyanobacteria provide details that might help investigators?