A multi-car crash on the Sydney Harbour Bridge has killed two men, injured a pregnant woman and resulted in traffic gridlock across the city.
The famed bridge partially reopened after 4pm on Thursday, almost three hours after the fatal five-vehicle collision.
Footage from bridge security cameras showed a northbound vehicle veering into southbound lanes about 1.40pm, triggering a series of collisions between three cars and a coach.
The man in the northbound car and a male driver of another car died at the scene.
Two other people were taken to hospital with minor injuries, including a pregnant woman.
Police were cautious about providing more details, including the ages of the dead men, until their families were notified.
The crash on a critical arm of Sydney's motorway network shut the bridge in both directions, leading to bumper-to-bumper traffic snaking up to 12km from the scene.
Delays were also felt on other routes as heavy vehicles unable to use the Harbour Tunnel were forced into a lengthy detour.
Transport for NSW co-ordinator-general Howard Collins urged any commuters to avoid driving on Thursday evening if they could.
That included the tens of thousands headed to US rapper Travis Scott's sold-out concert at Sydney Football Stadium.
"One less motorist on the road will help us move people, which includes ambulances ... and my (firefighter) colleagues as well," Mr Collins said.
Acting Superintendent Clayton McDonald said it was not clear why the northbound driver veered into oncoming traffic.
No arrests have been made over the crash, although a motorcyclist was arrested after driving through stopped traffic and into the cordoned-off crash scene.
"That gentleman drove towards police who stood in front of him and were able to stop that gentleman," Supt McDonald said, adding one officer suffered grazes during the arrest.
He said the motorcyclist had a suspended licence and the motorcycle appeared unregistered.
The bus driver, who was driving an empty vehicle, was uninjured.
