Human remains found in a mineshaft in a Bacchus Marsh park have been identified as those of missing teenager Cayleb Hough, who was last seen in December last year.

The remains were found in a shallow mineshaft near Seerey Track in the Lerderderg State Park on March 10, and have since been formally identified.

Cayleb's death is being treated as suspicious.

The 17-year-old was from the south-east Melbourne suburb of Chelsea Heights and was last seen in the nearby suburb of Highett on December 20.

Police believe he had been travelling in a blue 2003 Ford Falcon sedan, which was later found in the car park of a Southbank entertainment complex on January 16 and seized.

Police have released images of clothes similar to those Cayleb Hough had been wearing when he was last seen. (Victoria Police)

Missing Persons Squad Detective Senior Sergeant Craig Rhodes has today appealed for public help, especially from anyone who visited the park.

"We are particularly keen to speak to anyone who may have seen any suspicious activity in the Lerderderg State Park since 20 December 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.

"Cayleb’s family deserve some answers in relation to this horrific tragedy."

Police have also released images of clothing similar to the items Cayleb was wearing at the time of his disappearance.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000.

This is a developing news story.