Homicide squad detectives have arrested and questioned a man over the disappearance of Melbourne schoolgirl Siriyakorn 'Bung' Siriboon more than two years ago.

The ABC can reveal that the 24-year-old local man has claimed he hit and killed the Boronia Heights College student while driving in his car on the morning she disappeared, then panicked and disposed of her body at a local reserve.

The man - who the ABC has chosen not to name - was first arrested and interviewed in August, leading police and emergency services personnel to search the Old Joe's Creek retarding basin for a week.

Although the search yielded nothing, homicide squad detectives told the ABC they have also seized "items of interest" from the man, and that they are being forensically tested.

They would not describe the items, but one is believed to be the man's car.

The man was questioned a second time in October, and was described this week by police as still a "person of interest".

They also revealed another man was arrested and questioned last year over Bung's disappearance.

Police stressed that the 24-year-old is not the only suspect, and again urged the public to contact Crime Stoppers with information about Bung's fate.

The ABC revealed in October that Victoria Police was shutting down the Puma taskforce, which was set up to investigate Bung's disappearance.

Senior police stressed that the dismantling of the squad did not mean police had scaled back the investigation or given up hope of finding whoever is responsible for Bung's disappearance.

"We've met with Bung's family and explained to them that the investigation is still very much active and we remain committed to providing them with some answers," Detective Superintendent Tess Walsh said at the time.

"If new information is received or the investigation gets to the stage where we need to draw on additional resources, we have the ability upscale our response if needed.

"The taskforce detectives have worked tirelessly on this investigation and I am confident that the homicide squad will continue that and we will find out what happened to Bung."

Task force detectives interviewed more than 250 registered sex offenders, canvassed more than 1,000 Boronia homes and investigated more than 1,100 pieces of information and reports generated from calls to Crime Stoppers.

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