Breaking: Multiple people injured in bus crash in Perth's north

A bus crash in Wanneroo has injured several people, at least one critically. (ABC News: Mya Kordic)

One person suffered critical injuries when a bus collided with a tree on Joondalup Drive in Wanneroo in Perth's north.

Another four people were taken to hospital after being hurt in the crash.

The accident comes after a car collided with a pedestrian before crashing into a hospital in Perth's south, forcing the closure of its emergency department.

Multiple passengers have been hurt after a Transperth bus crashed into a tree in Perth's north, with at least one person critically injured.

A St John WA spokesperson said at least five people had been taken to hospital after the accident, which happened just after 11am on Joondalup Drive in Wanneroo.

At least five people were injured when a bus crashed into a tree in Wanneroo. (ABC News: Mya Kordic)

One of those passengers is in a critical condition at Joondalup Hospital, while another passenger was transported under priority one conditions to Royal Perth Hospital.

Three other passengers are being treated for non-life-threatening injuries.

The accident caused heavy traffic in the area. (ABC News: Mya Kordic)

Pictures show the front of the bus was significantly damaged after smashing into the tree.

Police remained at the scene on Thursday afternoon, with forensics officers marking up Joondalup Drive as they try to piece together what happened.

Police are trying to find out how the accident happened. (ABC News: Mya Kordic )

The crash forced the closure of Joondalup Drive between Burns Beach Road and Wanneroo Road, with motorists asked to avoid the area.

The incident happened about an hour after a car crashed into St John of God hospital in Murdoch, in Perth's south, forcing the closure of its emergency department.

A car crashed into a treatment ward at St John of God Murdoch Hospital on Thursday morning. (ABC News: Cason Ho)

Police say a grey Nissan Tiida sedan was involved in collision with a 73-year old male pedestrian before it smashed into the outside wall of a treatment ward just after 10am.

The pedestrian was taken to Royal Perth Hospital with critical injuries, while the 83-year-old male driver of the car is receiving treatment for minor injuries.

Aphrodite Bouari was attending an appointment at the hospital when she said she heard a loud bang. She initially believed it was construction noise.

Aphrodite Bouari was attending an appointment when she heard a loud bang. (ABC News: Cason Ho)

"So I didn't think of anything at all, and then when I came out, I'm like, oh my God," she said.

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