Traffic chaos has broken out in Perth’s north where at least five vehicles have been involved in a crash after a driver had a medical episode.

Multiple lanes have been shut as emergency crews respond to the crash, which was reported just after 11am on Saturday.

First responding vehicles have blocked traffic across lanes on Morley Drive heading west at Flinders Street in Nollamara.

Police said several vehicles were involved in the crash, including a motorbike.

St John Ambulance is at the scene.

It’s not yet clear how many people have been injured.

More to come.