A WA Police Force spokesman told local media: "[We are] aware of the presence in Western Australia of a small number of people with links to the Mongrel Mob street gang.
A Facebook page bearing the name "Mongrel Mob Australia'' has also been set up.
It includes photos and videos of patched members on motorcycles and wearing their signature black and red.
The posts go far back as 2014.
Images of the gang's patches - which usually carry the names of New Zealand areas - start to show Australian city names, such as Melbourne and the Gold Coast, in 2015.
In a message posted to the page that same year, in April, it reads: "Just because this...the NZ based chapter, doesn't mean we ain't here. lol. I'm telling you now, the Mighty Mongrel Mob nation are here and here to stay.
"Playing it smart and [keeping] it in stealth mode until it's time to let our Dogg [Soldiers] into public!'' (sic)