Acacia Prison manager Serco has dismissed two prison officers as an investigation into drug smuggling in WA prisons continues.

The two custodial officers at the facility were stood down from duty following a year-long joint investigation between the Corruption and Crime Commission, the Department of Justice and WA Police for allegedly "engaging in serious misconduct".

The investigation has aimed to uncover improper relationships between prison officers and prisoners, and the smuggling of drugs and other contraband into WA's prisons.

A Serco spokesman confirmed the two officers had been officially dismissed on Friday afternoon.

"Acacia Prison has worked closely with the CCC to support their investigation, and has dismissed two staff members with immediate effect," he said.

"We expect high standards of integrity from our staff, the vast majority of whom are hardworking and honest. We have zero tolerance for any actions that compromise safety in prisons or the wider community."

Corruption and Crime Commissioner John McKechnie QC told Radio 6PR the officers had been penalised after "disturbing evidence" revealed during a private investigation.

"We've received disturbing information and evidence about the ease with which serious drugs and steroids can be smuggled into prisons, the lack of proper security checks on that and the ability of some prisoners to attempt to groom some prison officers outside – [that is to] make relationships that they then use to subvert the officers," he said.

"The commission has been running a cooperative investigation for many months. It has been an, and still is in one sense, covert.

"But we've received disturbing evidence in private investigations and this is people's chance to come forward voluntarily before we come and knock on their door.

"This particular operation is at Acacia but we are also looking at a number of prisons in Western Australia."

When asked if it was likely the two prison officers were alone in their misconduct, Mr McKechnie was blunt:

"No," he said.

"The CCC is looking. People have two choices.

"If they think they've been doing the wrong thing and they want to come and tell us, we're more interested in the systemic problem and they can come and tell us.

"But if they don't tell us, it's double or nothing. They might not know that we're already looking and listening."

The WA Prison Officers Union said it would continue to aid in the investigation.

"The WA Prison Officers Union acknowledges the CCC investigation... is ongoing. WAPOU respects the independence and authority of the CCC, and will cooperate fully with the investigation if and as required."