Police have charged a former detective with murder, and are searching for another, over the disappearance of a Sydney student six days ago.

Jamie Gao, 20, is understood to have been taking part in a drug deal when he was last seen getting into a white car after talking to two men in Padstow in the city's south-west last week.

Officers say Mr Gao had drugs on him when he got into the car and was driven to a nearby location where they believe he was killed.

A body was found off a beach near Cronulla this morning, but police are yet to confirm if it is the remains of Mr Gao.

Former detective Glen McNamara, 55, was charged with murder and commercial drug supply at St George Police Station and made a brief appearance at Kogarah Local Court in Sydney's south this morning.

Mr McNamara's lawyer told the court his client wished to be placed in protective custody.

The ABC has been told officers are also searching for notorious former detective Roger Rogerson, 73, who is believed to be in Queensland.

Detective Superintendent Luke Moore said police would allege Mr Gao was killed as part of a drug deal. He said almost three kilograms of what was believed to methamphetamine had been found.

Glen McNamara is escorted out of Kogarah local court in Sydney on Monday afternoon. ( AAP: Daniel Munoz )

Detectives have seized three cars, including a blue Ford Falcon and a white Ford Falcon, as well as a boat from properties in Sydney's south as part of their investigation.

Police are still looking for two Asian males who were in Mr Gao's car on the day of his disappearance.

"He [Mr Gao] had two other Asian male people with him in that car. We know that shortly after arriving there, he walked from that car to another white motor vehicle, a white station wagon," Mr Moore said.

"He got into that car. That car then drove from that area and was followed by a silver station wagon. We know that Mr Gao was taken to a location nearby. At that location we believe he was murdered.

"The purpose of the meeting we now strongly believe, and will be putting to the court, was for a drug transaction - a substantial quantity of prohibited drugs. We will be putting to the court that that was the subject of the drug transaction."

McNamara, who was taken into police custody after his vehicle was stopped in Kyeemagh in southern Sydney last night, was remanded in custody when he appeared in a Kogarah court today.

Police have searched properties in Cronulla and Padstow.

Police believe Mr Gao may have met with foul play after getting into the vehicle. His own car was later found abandoned with his wallet, keys and phone nearby.

Police say they have been told Mr Gao was excited about the arranged meeting and his disappearance and lack of contact are out of character.

Mr Gao has been described as about 170 to 175 centimetres tall, with black hair and brown eyes.

Anyone with information on the disappearance is encouraged to call Crime Stoppers on 1800 333 000.



Rogue detective jailed on conspiracy charges

Rogerson was once one of the most decorated police officers in New South Wales, having been awarded 13 bravery awards.

He joined the police force in 1958 at the age of 17 but went on to be known as Australia's most notorious ex-police officer, and mate of underworld figures such as Neddy Smith.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 7 minutes 1 second 7 m Two former NSW detectives linked to university student's murder

Mr Rogerson became infamous in the 1980s for his alleged crimes and misdemeanours.

During that decade he was called 'Roger the Dodger'. During this time Mr Rogerson protested his innocence and insisted he was the victim of a vendetta waged by a group of police officers out to get him.

In an interview with the ABC in March 2006 he said: "There's many blokes I locked up for crimes I liked; I had to admire their strength and their tenacity. You know, I wouldn't do it, I wouldn't be game to do some of the things that some of these blokes have done. So look, yes there was a bit of admiration there, but it was a job."

In 1986 Mr Rogerson was dismissed from the NSW police force and charged with conspiring to pervert the course of justice.

Former NSW detective Roger Rogerson in 2004 ( AAP: Rob Hutchison, file photo )

In 1990 he was convicted of conspiracy charges relating to an attempt to frustrate a police investigation into two bank accounts, opened in 1985 under false names, which contained $110,000.

His conviction was overturned by the Court of Criminal Appeal after he had served nine months of a six-year jail term.

The High Court then overturned his acquittal. So he appealed again.

In 1992 he lost that appeal but his sentence was reduced from six to three years' jail.

In 1993 Mr Rogerson appeared before the Independent Commission Against Corruption (ICAC), which was reinvestigating allegations he helped criminal informant Neddy Smith to check out if a large quantity of gold coins had been reported as stolen.

The allegations had come to light before the Police Integrity Commission 10 years previously, and Mr Rogerson had been acquitted.

In 1995 he was released from Berrimah jail, only to return in 2005 when he was sentenced to two-and-a-half years in jail for lying to the Police Integrity Commission.

He pleaded guilty to lying while under oath when he told the Police Integrity Commission he did not know about bribery at Liverpool Council in 1999.