Police in Rio de Janeiro have arrested the former boyfriend of slain mining executive Cecilia Haddad.

Mario Santoro, 40, was found hiding at a relative's house in the city's Botafogo district.

Brazilian police issued an arrest warrant for Mr Santoro this weekend, following high-level negotiations with Canberra.

A NSW Police spokeswoman said homicide squad detectives were ready to travel to Brazil "as soon as international protocols were met".

"The NSW police force is continuing to work through Commonwealth processes in order to bring a successful conclusion to their investigation," the spokeswoman said.

Mario Marcelo Santoro (left) is Cecilia Haddad's former boyfriend. ( ABC News )

She said it was not appropriate to comment on diplomatic arrangements.

A spokesperson for the Federal Attorney-General Christian Porter said the arrest was a matter for Brazilian authorities.

"Australia does not comment on extradition matters including whether a request has been made or it intends to make a request," the spokesperson said.

The body of Ms Haddad, 38, was found in Lane Cove River in Sydney's north just a day after friends reported her missing in April.

Suspicions were raised immediately as Ms Haddad was found fully clothed, with weights inside each pocket of her cargo pants.

Mr Santoro left for Brazil the same day Ms Haddad's body was discovered.