A man has died after jumping into the Parramatta River while running away from officers, police say.
Police said they have formed a critical incident investigation into the circumstances surrounding the man's death.
Officers from Rosehill were patrolling the Ermington area, in Sydney's west, when they stopped a taxi about 4.20am on Thursday.
A man and a woman who were passengers in the taxi got out of the vehicle and ran away, police said.
Police said the officers chased the man, who jumped into the river.
His body was found in the water shortly afterwards.
A critical incident team from Campbelltown Local Area Command will investigate, and will be overseen by the Professional Standards Command.
Police are appealing for any witnesses to call Crime Stoppers on 1800 333 000.
A NSW Police spokeswoman would not comment on why the taxi was pulled over.