Homicide detectives and local police are trying to establish whether Amesha Rajapakse's death is suspicious after the 31-year-old's body was found in water behind a set of Westmead unit blocks.

Police said her death was puzzling because of where her body was found but said there were no marks or obvious signs of injury on her body.

"The location she was found at was puzzling; it was hard to get to," a homicide detective said.

"But we really don't know one way or the other."

Building manager Tom Hailey said security footage captured the woman pacing back and forth in the foyer of a building inside Monarco Estate about 7.30pm on Tuesday.

"It looked like she was concerned about something; she appeared agitated. She kept going from back to the front of the foyer," Mr Hailey said.

Mr Hailey said residents told him they heard a "blood-curdling scream" about 6.30am on Wednesday just before police arrived at the Bridge Road unit block.

A man at the scene cried, "Please, please let me see her face", a short time after Ms Rajapakse was found.

Wearing muddied shoes, he fell to his knees as he hugged relatives in heavy rain.

Officers were seen searching the man's pockets before he got into a police car and was driven from the estate along with another distressed man.

Mr Hailey said relatives of the Sri Lankan-born woman had spent the previous night searching for her after she failed to return home to her seventh-floor unit.

Up to 40 police, including divers and public order and riot squad officers, spent much of the day scouring the muddied creek and searching the grounds of the unit complex.

Police said they would not be able to determine what caused Ms Rajapakse's death until they received initial autopsy results on Thursday.

They are appealing for anyone with further information to call Crime Stoppers on 1800 333 000.