The desperate family of a missing former elite police officer searched an industrial estate the day before his body was found, fearing the worst had happened.

Twenty-four hours later, their suspicions were confirmed when police found former Special Operations Group officer Dean McGrath lying dead inside a building in the Braeside industrial estate, about 26 kilometres south-east of Melbourne's CBD.

The 41-year-old former senior constable left the force in 2010 with post traumatic stress disorder.

A 45-year-old man handed himself in to a nearby police station on Friday morning, which led investigators to make the grim find on Governor Road just before 10am. He remained in custody on Friday night.