A car has ploughed 20 metres through the entrance of the Joondalup Health Campus in Perth's north, injuring six people, one seriously.

The incident was reported to police at 12:10pm.

A woman believed to be aged in her 80s drove into the front of the building, according to police.

A witness said the car had travelled 20 metres through the entrance and into the building, and smoke was billowing out.

Fire trucks were called to the scene of the crash. ( ABC News: Nicolas Perpitch )

A Joondalup Health Campus spokeswoman confirmed the car had crashed into the hospital's discharge lounge shortly after midday.

"We can confirm that at 12:05pm a car crashed into our discharge lounge where patients are awaiting transport home," she said.

"We actioned our emergency plan."

She confirmed a total of six people were injured in the crash, including the driver, a staff member and four patients awaiting discharge at the hospital.

Four of those injured have since been discharged from hospital, while the other two remain.

Of those, one is in a serious but stable condition and is being transferred to Royal Perth Hospital.

The other is at Joondalup in a stable condition.

An area has been cordoned off at the scene of the crash. ( ABC News: Nicolas Perpitch )

The spokeswoman confirmed the area impacted by the crash had been cordoned off, but the hospital remained open and ambulances had not been diverted.

Witness Lloyd White arrived shortly after the crash.

He said smoke was coming out of the building and people were panicking.

The spokeswoman said those affected were being offered counselling and support.