Three Perth police officers who tested positive to drugs while on duty have been stood down, it has been revealed.

WA Police's internal affairs unit tested about 200 officers at five suburban police stations on Monday.

According to a police statement, three officers returned "a presumptive positive result to amphetamine and methylamphetamine".

The results have been forwarded to the WA Chemistry Centre for analysis and confirmation of the result.

WA Police Commissioner Karl O'Callaghan said it was important that police officers were scrutinised.

"We had for some years been negotiating with the union to introduce drug testing, and there was a bit of resistance to it," he said.

"But I pushed very hard because I believe police officers are out there, they're using weapons, they're dealing with the public and it's really important that like any industry — for example mining — we also test our officers for drugs and alcohol."

He said the results were a concern, but the numbers were low.

"We have to look at this in context, you know there's more than 6,000 officers working the West Australian police, and in the three years since 2012 we've identified just 10, so it's less than half of 1 per cent," he said.

"It's small but I guess it's reflective of what we're seeing in the wider community."

According to police, since legislation allowing random testing was enacted in 2011, about 9,500 screenings have been carried out on police officers.

Of those, 11 had been found with a blood alcohol limit of more than 0.02 per cent, two were found using cannabis, two using MDMA, two on steroids and one on methamphetamine.

"Six of the officers who tested positive to drugs resigned prior to the conclusion of a Loss of Confidence Process," the statement said.

"The seventh received a Letter of Corrective Advice after it was accepted he may have unwittingly ingested the steroid in an exercise supplement."

Those results do not include the three officers stood down following Monday's operation.

Commissioner O'Callaghan said if the latest three officers caught had their tests confirmed as positive for amphetamines, they would lose their jobs.