Bus driver may have had medical episode before crash that killed 61yo man

The Transperth bus speared into the large tree, leaving the front of the vehicle a mangled wreck. (ABC News)

A 61-year-old man who was one of seven passengers injured when a Transperth bus smashed into a tree in Wanneroo has died in hospital.

A 59-year-old woman who was critically injured in the crash remains in a serious condition, and it is understood the 56-year-old male driver is also still in a serious condition.

Police are investigating whether the bus driver suffered a medical episode that caused him to lose control, and say inquiries into the crash are ongoing.

A 61-year-old passenger who was critically hurt in a bus crash in Perth's northern suburbs has died from his injuries, and police are investigating whether the driver suffered a medical episode.

The man was one of seven passengers injured when the driver of the Transperth bus lost control on Joondalup Drive in Wanneroo around 11am on Thursday and crashed into a tree.

He was taken to Joondalup Health Campus for treatment and later transferred to Royal Perth Hospital (RPH), but died overnight.

The bus crashed into the tree on Joondalup Drive late on Thursday morning. (ABC News: Mya Kordic)

A 59-year-old woman who was critically injured in the crash remains in RPH in a serious condition.

The driver, a 56-year-old man, was also taken to RPH, and it is understood that he remains in a serious condition.

Emergency services rushed to the scene to help those injured in the accident. (ABC News)

One of them, a 26-year-old man believed to have been seated at the back of the bus, has been discharged from hospital.

Police blocked off the area as emergency services responded to the crash. (ABC News: Mya Kordic)

Police are yet to confirm what caused the driver to lose control of the bus.

One witness who was driving nearby and rushed to help said she saw the bus swerve into the opposite side of the road and then crash into the tree.

WA Transport Minister Rita Saffioti said police were investigating the circumstances of the crash.

Rita Saffioti says bus CCTV footage is being examined to help pinpoint the cause of the crash. (ABC News: Keane Bourke)

"This was a tragedy for everyone involved … my sympathies and condolences go out to the families," she said.

"[Police] are investigating whether this was a medical episode.

"There is CCTV onboard, that will help in understanding exactly what caused that crash."

Police are investigating whether the bus driver had a medical episode. (ABC News: Mya Kordic)

When asked whether there was a need for more safety measures on buses, Ms Saffioti said po