Two men are in a critical condition after the light plane they were in crashed onto an oval at South Lake in Perth's southern suburbs.

Police say the single-engine plane took off from nearby Jandakot Airport at about 2:30 pm.

Senior Sergeant Glenn Swannell says he believes the plane had engine trouble shortly after take-off, and it headed for open ground.

The pilot managed to avoid nearby powerlines but clipped a football goalpost before the plane ploughed into the field.

"I can only presume that the pilot had enough skill to fly under the powerlines and bring it to the ground on the oval," he said.

The plane crashed on the oval near Berrigan and Elderberry Drives, and then burst into flames but the two men managed to clamber out before flames engulfed the wreckage.

Witnesses see men clamber out of wreckage

Witnesses reported seeing the two men, who are thought to be in their 50s, exit the plane and could see their clothes were on fire.

Two nearby residents, one of whom is a firefighter and the other an off-duty ambulance officer, were the first on the scene and helped treat the two injured men.

Another resident Liam watched the scene unfold.

"It came in, tried to do a bit of a landing, then bang, explosion, things on fire," he said.

"There were choppers in the air, a plane come down, it was on fire, police and people everywhere, crazy, crazy, crazy."

A school student, Jordan Kennedy, also witnessed the crash.

"I just heard it come down and go bang, and then see all the smoke," he said.

The Education Department says the crash did not occur at Lakeland Senior High School but at a nearby council oval.

A teacher says the school does use the council oval but the students who would have ordinarily been on it at the time the plane crashed chose to go bowling today instead.

One of the men was transported to hospital by ambulance while the rescue helicopter transferred the other to RPH.

Senior Sergeant Swannell says an investigation is likely.

"We're waiting on advice from the Air Transport Safety Bureau to see if they're going to attend," he said.