Assistant Commissioner Nick Anticich raised concerns about the gang eyeing off the WA drug market when addressing hundreds of lawyers at a convention of prosecutors last July.
This week, he said police were aware Notorious members had been to WA.
"Notorious have had no established premises and/or presence in Western Australia but we are aware of members who have been to WA," Mr Anticich said.
"It is suspected that these visits were related to establishing a presence or conducting crime-related business.
"Reliable intelligence indicates that some larger amounts of drugs coming into Western Australia from eastern Australia have been facilitated by persons linked to members of that organised crime group.
"While Notorious does not have a permanent presence in WA, it does appear likely that they have been involved in supplying drugs to a high-price market here in WA.
"The Perth price for amphetamines is between double and triple the price on the eastern seaboard."
Mr Anticich said Notorious came to prominence about 2007 around Sydney with a membership drawn mainly from the Nomads outlaw motorcycle gang and youths of Middle Eastern background.
Reports from the east suggest Notorious rose from a splinter group of the Nomads and gang members have been fighting for control of Sydney's Kings Cross.
That struggle has included shootings at property linked to rival gang members and the bombing of a Hells Angels' clubhouse in an apparent revenge attack.
Eastern States newspaper reports describe Notorious as the "Nike bikies" because of a preference for high-end sport sneakers, brand-name T-shirts and clean shaven appearances rather than the stereotypical image of a leather-clad bikie with a bushy beard. They were also called bikies without bikes.
There has been a marked rise in gangs in WA in recent years, with two - the Finks and Rock Machine - having bloody fights with established WA gangs.