A former NSW detective has been charged with the murder of a missing Sydney university student and police also want to speak to disgraced detective Roger Rogerson over the disappearance.

Glen McNamara, 55, who was stationed at Kings Cross during the late 80s, was charged with the murder of Jamie Gao, early Monday morning.

Police are also searching for Rogerson, an associate of Mr McNamara, to question him relation to the missing 20-year-old. He is reportedly in Queensland.

Mr Gao, from Hurstville, has been missing for five days after getting into a white car with two men in Padstow on Tuesday afternoon.

Police suspect he has got ''in over his head'' and was kidnapped and killed after arranging a ''secretive'' meeting with an unknown party.

Mr Gao was last seen about 1.40pm on Tuesday getting into the car on Arab Road in Padstow shortly after speaking to two men, both described as being of Asian appearance. He was carrying a bag.

Mr Gao's own car, a white Nissan Silvia sedan, was found abandoned nearby with his phone, keys and wallet.

On Sunday, Detective Superintendent Luke Moore from the robbery and serious crime squad said the circumstances of Mr Gao's disappearance suggested foul play.

Hours later Mr McNamara was pulled over during a traffic stop at Kyeemagh in Sydney's south and he was questioned overnight before being charged with murder and drug offences.

Mr McNamara is a former investigator with the National Crime Authority and the NSW Police, where he was a detective stationed in Kings Cross and Sydney's south. He gave evidence to the NSW Police Royal Commission about alleged police protection of paedophiles.

Rogerson, 73, was a decorated senior police officer until he shot dead drug dealer Warren Lanfranchi in 1981.

He was later accused of supplying drugs, assault, bribery and conspiring to murder, but was never convicted.

He was twice convicted for lying in court and served two separate jail terms.

Mr McNamara will face Kogarah Local Court on Monday.