The homicide squad is investigating a man believed to be an ex-boyfriend of Brazilian businesswoman Cecilia Haddad, the 38-year-old found dead in the Lane Cove River on Sunday.

Police did not reveal details, only that the man was in Sydney at the weekend and has since returned to Brazil.

Key points: Cecilia Haddad was a former mining executive turned business consultant

Cecilia Haddad was a former mining executive turned business consultant The Brazilian national was last seen on Friday at a BBQ, but spoke to friends on Saturday morning

The Brazilian national was last seen on Friday at a BBQ, but spoke to friends on Saturday morning Police are asking for any CCTV or dashcam footage of Ms Haddad or her car

Homicide detectives are treating the circumstances surrounding the death of Ms Haddad — a former mining executive — as a possible murder.

The Brazilian national's body was found in the water in Woolwich, near Angelo Street, on April 29 about 10:15am.

Police said Ms Haddad, who worked as a supply chain manager for mining company BHP Billiton in Western Australia before moving to NSW in 2016.

While in Sydney, she ran a consultancy business and worked as a logistics manager for a freight company.

She also and had an active social life and a large circle of friends, police said.

More recently, she had been volunteering as a disability support worker with Hireup since August last year.

CEO, Jordan O'Reilley, said the company's thoughts were with Ms Haddad's family and friends.

Cecilia Haddad, 38, was last seen at a barbeque on Friday night. ( Supplied: NSW Police )

"She was a bright and valued member of our team. Her services and positive approach were much valued by our community," he said.

Ms Haddad, who lived in Ryde, was last seen at a barbeque last Friday night and then spoke to friends on the phone between 8:00am and 9:30am on Saturday, police said.

Her friends raised concerns about her welfare when she failed to appear at a number of appointments on Saturday.

Her car — a red 2013 model Fiat 500 sedan with a black roof — was located by police at West Ryde train station on Sunday afternoon.

However, they were unable to say whether she drove the vehicle there herself.

Police are awaiting the results of an autopsy but were reluctant to speculate on her cause of death.

'Completely out of character'

The State Crime Command's Homicide Squad and Ryde Police Area Command have formed Strike Force Bronwyn to investigate the circumstances surrounding her death.

"By all accounts, Cecilia enjoyed an active social life and had made a large circle of friends during her time in Sydney," Detective Acting Inspector Richie Sim.

"Police spoke to a number of friends and associates in those initial stages, who described it as completely out of character.

The apartment building where Ms Haddad lived was attended by police today ( ABC News: Brooke Wylie )

"We've been told her vehicle was seen outside her home on Saturday afternoon, so we are very keen to speak with anyone who may have seen her or her vehicle after that time."

Ms Haddad's vehicle registration is DJV50H.

"We are specifically seeking CCTV or dash-cam footage of Cecilia or her vehicle, possibly in the Hunters Hill, Ryde, Top Ryde, West Ryde, and Woolwich areas over the weekend," Inspector Sim said.

"While we are awaiting the results of a post-mortem examination, which is expected to take place today, we are treating her death as suspicious."

On her LinkedIn account, Ms Haddad listed her most recent role as the managing director of CHC Consulting firm based in Sydney.

She was also the head of operational planning at freight company Pacific Planning.

Her credentials include a Master degrees from the Pontifical Catholic University of Rio de Janeiro and a certificate from the University of Tasmania.