Brazilian police have arrested Mario Marcelo Santoro over the death of  former girlfriend Cecilia Haddad, whose body was found in Sydney’s Lane Cove River – but his extradition to Australia is far from certain.

The Rio de Janeiro police department said Santoro was arrested at a relative’s home in the city’s Botafogo district on Saturday, the Associated Press reports.

Local footage shows Santoro being led through a frenzied media pack on his way into a police station.

He was arrested a day after police searched his home in Rio de Janeiro, as well as those of his parents and relatives, after a warrant for his arrest was issued on Thursday.

Santoro flew back to his native Brazil on the same late April weekend the 38-year-old Brazilian mining executive’s fully-clothed body was found in the Lane Cove River.

NSW Homicide Squad detectives are preparing to travel to Brazil “as soon as international protocols have been met”, a police spokeswoman told AAP.

“NSW Police Force is continuing to work through commonwealth processes in order to bring a successful conclusion to their investigation,” the spokeswoman said.

A warrant for the 40-year-old’s arrest was issued last month, but there are concerns Santoro will never be extradited to Australia to face charges because of Brazilian laws and customs.

Casting a shadow over his possible return to face trial is the precedent of Great Train Ronnie Biggs, who was found in Rio years after his escape from a British prison.

A Brazilian ruled against Scotland Yard’s extradition request on the grounds that Biggs had established “family ties” in the country after fathering a cxhild with his stripper girlfriend.

Fabio Cardoso, from Rio’s homicide division, said police believe Ms Haddad was killed by asphyxiation.

“In April, by not accepting the break-up, he (Santoro) allegedly killed her by asphyxiation by pressing her neck and dumping her body in the river,” Mr Cardoso told the Seven Network in Brazil.

“He had the key to her house because he lived there for a while.”

Foriegn Minister Julie Bishop last week told reporters Australian authorities were “working closely” with Brazilian counterparts to ensure an “appropriate” outcome.

-with AAP