The heartbroken parents of missing four-year-old Gus Lamont have pleaded for anyone who knows anything about his disappearance to come forward.

Parents Josh and Jess released a statement through South Australia Police on Tuesday, begging for information about their son.

“We are united in our grief, and we are united in our search for answers about what happened to our little boy, Gus, who means everything to us. Our lives have been shattered, and every moment without him is unbearable,” they said.

“We know someone out there may have information. If someone knows what happened, we are pleading with that person – or anyone who may have seen or heard anything – to please come forward. Even the smallest detail could give us the answers we so desperately need.

There has been no trace of the little boy since he vanished from the family’s remote homestead in South Australia’s Mid North, more than 300 kilometres north of Adelaide, on September 27.

Gus’s parents say they have been shattered by his disappearance. Photo: SA Police

SA Police have returned to the remote Oak Park Station numerous times, including last week, searching buildings and structures and other locations adjoining the property.

Officers have also searched old mine shafts and inspected an outhouse where fresh cement had been laid and a water tank at a neighbouring property.

A police helicopter assisted along with the cadaver dog but no evidence was located.

Previously dams have been drained and investigators have seized items from the station homestead, including a vehicle, a motorcycle and electronic devices, for forensic testing.

The intensive searches for Gus have spanned almost 500 square kilometres and involved hundreds of police and volunteers as well as aerial support and mounted units.

Early in February, police declared Gus’s disappearance a major crime and said someone living at Oak Park was a suspect in the case and his likely death.

They confirmed the boy’s grandparents, his mother and his younger brother were at the property at the time he disappeared. They have emphasised his parents are not suspects.

Last week, SA Police Commissioner Grant Stevens played down the possibility of an imminent arrest in the case.

“I haven’t been briefed on the potential for that outcome but given the complexities around this particular investigation, it is a fair assumption that we will be working on the disappearance of Gus for some time to come yet,” he said.

“We’re not ruling out anything. Adjoining properties, including the national park, will form part of our investigation as we move forward.”

The vast search has included draining dams and searching mineshafts. Photo: SA Police

Also last week, police arrested one of the boy’s grandparents and charged them with firearm offences. The charges are unrelated to the investigation into the little boy’s disappearance.

The name of that person has not been released. They are due to appear in the Peterborough Magistrates Court on May 6.

Stevens said police would use every resource available in the search for Gus.

“I think it’s reasonably foreseeable that we will be visiting Oak Park quite frequently over the coming months as we continue our investigation as well as visiting surrounding locations in the vicinity of the residence,” he said.

On Tuesday, Gus’s parents also released a video and new photograph of the missing boy. They also thanked those who had helped search for him.

“The tireless efforts of police, emergency services, ADF personnel, volunteers, and specialists have meant more to us than we can ever say,” Josh and Jess said.

“To the friends, family and supporters who have shown such compassion, concern, and assistance during this heartbreaking time: Thank you. Your kindness has helped carry us through the darkest days of our lives.

“All we want is to bring Gus home and understand what happened to our beautiful boy”.