Human remains have been discovered at a Geelong property that belongs to the family of missing man Daniel O'Keeffe.

Key points: Mr O'Keeffe vanished from his Geelong home in 2011

Mr O'Keeffe vanished from his Geelong home in 2011 Police cannot say why the remains were not discovered in searches of the property

Police cannot say why the remains were not discovered in searches of the property Family say they have "heavy hearts" after find

The remains were found at the Summerhill Terrace home in Highton in the city's west just after 1:50pm and detectives are still at the scene.

A crime scene was set up after the family discovered the remains and informed Victoria Police.

Police have confirmed the remains are that of an adult, but said formal identification still needed to be undertaken.

In a statement on Facebook the family confirmed the discovery.

"It is with heavy hearts that the family and friends of Dan O'Keeffe update this page to share that Dan's remains were discovered earlier today," they said.

Mr O'Keeffe was 24 when he vanished from his Geelong home in 2011 without taking any belongings.

His parents had set up a website and launched the Dan Come Home social media campaign, as part of a high-profile effort to find him.

Detective Sergeant Adam Forehan said the remains were found under the house.

"We're treating it at the highest level at this stage until we satisfy ourselves that there is no suspicious activity," he said.

Police could not say why the remains were not discovered when they first searched the family property.

Police near the scene where human remains were found at the O'Keeffe family home. ( ABC News: Cameron Best )

Detective Sergeant Forehan said the family was extremely distraught at the find.

The O'Keeffe family launched a strong social media campaign in an effort to find him. ( Facebook: Dan Come Home )

"You can only imagine the feeling one would go through when discovering the remains of what you believe to be your beloved son," he said.

In the five years he was missing, there had been suspected sightings of Mr O'Keeffe in Queensland and Western Australia.

Detective Sergeant Adam Forehan said he could not shed much light on the reports.

"There can be no definitive answer given, let's just say opinions differ," he said.

Mr O'Keeffe's sister Loren devoted herself to finding him.

In 2013 she founded an organisation called the Missing Persons Advocacy Network to provide practical support for friends and families of missing people.

On the Dan Come Home Facebook page, Mr O'Keeffe was described as "friendly, gentle, thoughtful and very personable" and had suffered from depression.

It said he had mentored young people and competed in an overseas jiu-jitsu championship.