A MAN who started an out-of-control fire in Perth's outer suburbs has offered an apology on live television, thanking all of those who rushed to the scene.

Identified as James, the man was asked by Nine reporter Kamin Gock this morning to explain what happened yesterday afternoon in Baldivis, about 45km south of Perth's CBD.

"Basically (I was) coming down the road and the wheel bearing collapsed," he said, standing next to his boat and trailer on the side of Karnup Rd.

"And it started a small fire and it was, with the winds, I just couldn't put it out.

"Then it just took off to the other side of the road. Then I rang up triple-0 and yeah, before I knew it, it was out-of-control."

Emergency WA on Friday morning said the fire was still at watch and act alert level "due to unfavourable wind conditions which may cause the fire to breach containment lines".

The first alert for the fire was issued at 12.38pm on Thursday. It had reached emergency level within 25 minutes and remained at that status throughout the night.

Department of Fire and Emergency Services Superintendent Ray Buchan told the ABC there was spotting 300 to 400 metres ahead of the fast-moving fire, which had been travelling about 2.5 kilometres per hour.

He confirmed it started by a wheel off a trailer and sparks from it dragging along the ground.

"So we're classing that as accidental," Supt Buchan said.

Friday's alert was for people in the area bounded by Mortimer Rd and Gossage Rd to the north, Kwinana Freeway to the west, Karnup Rd to the south, and Kargotich Rd to the east, but not including the Freeway.

Parts of Mundijong, Hopeland, Olbury, Mardella, Serpentine, Baldivis, Wellard and Cardup in the City of Kwinana, City of Rockingham and Shire of Serpentine-Jarrahdale were warned.

"There is a possible threat to lives and homes as a fire is approaching in the area and conditions are changing," Emergency WA said in its alert at 9.29am Perth time (12.29pm AEDT) on Friday.

"If you are not prepared or you plan to leave, leave now if the way is clear."

Residents who are not at home have been told "do not try to return" as conditions in the area could be very dangerous.

James said he wanted to thank "all the fireys involved, the police and volunteers".

"I apologise to anyone that was affected by the fire," he said.

"Homes, or smoke, I sincerely apologise. I still feel sick about it now."

He said he believed speaking on live television was "the right thing to do".

"I know the arson squad said 'Mate, it's an accident, don't worry about it' but I still feel personally responsible," James said.

" So I just apologise and would just like to thank everybody involved. Helicopter pilots, everybody. As I said, I sincerely apologise."

In addition, a bushfire advice alert has been issued for parts of the City of Cockburn, City of Armadale, City of Kwinana, City of Rockingham and the Shire of Serpentine-Jarrahdale.

An evacuation centre has been established at Mike Barnett Sports Complex in Rockingham.

WA Member for Baldivis, Reece Whitby, visited the centre overnight and was among those to share images and vision of the blaze on Twitter.