Fire and rescue crews were called to the factory in the southern suburb about 10.30am.

Nearby residents have been urged to stay indoors and switch off their air-conditioning as thick smoke continues to blow in a north-easterly direction from the fire towards the suburb of Willagee.

Stock Road between South Street and Leach Highway, and Peel Road between Chamberlain Street and Stock Road, have been closed as more than 40 firefighters continue to battle the inferno that engulfed the Western Meat Packers Group factory in McNeece Place.

The Fire and Emergency Services Authority has urged people in the industrial area between Stock Road, Peel Road, Garling Street and Weatherburn Way to leave the area and go home for the rest of the day.

Also, residents on roads including Stock Road from Garling Street to Leach Highway, Leach Highway to North Lake Road, North Lake Road from Leach Highway to Stock Road, South Street from North Lake Road to Lander Street, and Lander Street from South Street to Garling Street should remain inside and turn their air-conditioning off.

Motorists are also being advised to avoid these roads.

At the moment, 45 firefighters and ten trucks from Belmont, Canning Vale, Daglish, Fremantle, Murdoch, Perth and Welshpool are trying to bring the fire under control.

The factory is the head office of the Western Meat Packers Group, which according to its website was established as a family business in 1983 and is now a major player in the meat industry.

The Department of Environment and Conservation's Pollution Response Unit is conducting air monitoring and analysis.