Police have launched a murder investigation after finding the remains of missing teenager Cayleb Hough in a mineshaft in a national park north-west of Melbourne.

The remains, which were found in the Lerderberg State Park in Bacchus Marsh on March 10, have been formally identified as Mr Hough’s.

Detectives will on Tuesday search the area with the assistance of the SES.

• Australia’s ‘best kept secret’ revealed
• Shorten’s humdinger of a zinger
• Australia needs high speed rail

Detective Senior Sergeant Craig Rhodes said Mr Hough probably knew his killer.

“This is tragic circumstances for the family,” he said.

“The hope was always there and the understanding was that he was a missing person.

“This has totally gutted the family, both the mother and the father, and it’s something they’re going to have to live with for the rest of their lives.”

There are a number of people of interest to police, but no suspects, Det Sen Snt Rhodes added.

Mr Hough was last seen near The Crescent, Highett, in the early hours of December 20.

In January, police found the car Mr Hough was travelling in when he was last seen.

The vehicle, which was found in the car park of a Southbank entertainment complex, remains in police possession as the investigation continues.

Det Sen Sgt Rhodes said Mr Hough’s family deserved answers.

“We are particularly keen to speak to anyone who may have seen any suspicious activity in the Lerderderg State Park since December 20 last year,” he said.

“Someone out there knows who is responsible for Cayleb’s death and we are appealing for them to come forward and contact police.”