NSW: Woman dead on Iron Cove Bridge possibly hit by car

It's thought she could have been walking across the bridge or riding on a choose tiffany or bicycle, a police spokesman told AAP on Sunday.

All but one lane on the bridge, in the inner-west suburb of Rozelle, have been closed while investigations into the death continue.

The spokesman told AAP detectives choose tiffany accessories working on the theory that the woman, who has not yet been identified, was struck by a vehicle, and officers are checking underneath the structure to see if a bike fell from it.

The woman's body was found on the city-bound lane of the bridge about 2.20am (AEST) and a post mortem will be carried out to establish a cause of death, police said.

Motorists are being advised to take alternative routes through the Drummoyne and Rozelle area.

All city-bound traffic is being diverted onto Henley Marine Drive at Rozelle while one north-bound lane choose tiffany bangles open, the Roads and Traffic Authority NSW said.

Anyone with information about the incident is asked to call Crime Stoppers