A man is in a critical condition in hospital after being bashed in a West Australian immigration detention centre.

The Department of Immigration and Border protection confirmed there was an "incident between several detainees" on Thursday at the Yongah Hill detention centre, next to the town of Northam, about 80km north-east of Perth.

Both Australian Federal Police and West Australian police, including detectives and a forensic team, were sent to the centre.

A witness said the man was in a compound of the centre largely reserved for convicted criminals awaiting deportation.

It is understood several of the assailants were from New Zealand.

A detainee who witnessed the attack said the victim was beaten inside the Falcon compound's television room.

"When they took him to hospital, he was still walking but he was bleeding," the witness said.

The man was initially taken to Northam Hospital, but then transferred to Royal Perth Hospital, where a spokeswoman said he was in a critical condition.

St John Ambulance said a doctor and a nurse had accompanied the man in the ambulance from Northam, as a priority one patient, amid concerns he may have head injuries.

Several detainees at Yongah Hill have told the ABC they believe the man is in a coma.

Serco 'took immediate action'

The immigration department said in a statement that detention service provider Serco was "providing the department with a full report into the circumstances of the incident".

"Law enforcement agencies have been informed," the statement said.

Serco said it was "committed to maintaining a safe and secure facility".

"Our officers took immediate action to de-escalate this incident and ensure that care could be provided to the individual as quickly as possible," the company said in a statement.

The Australian Federal Police have been contacted for comment.

WA Police referred enquiries to the Immigration Department.

Northam Shire president Steven Pollard said he did not know the exact circumstances of the incident but it was a concern.

"Obviously, any fighting or any incidents that require some sort of medical attention are a problem," Mr Pollard said.

"But I'm reasonably confident the department is on to the whole [issue], and they'll be looking into this incident and be making any adjustments as required."

Yongah Hill detention centre is now about half full of asylum seekers and half full of people detained for visa compliance breaches.

They include non-citizens who were sentenced to 12 months or more jail in Australia, have served their sentence and now face deportation under section 501 of the Migration Act.

People who have committed armed hold ups and been convicted of child sexual assault are among the section "501" detainees inside Yongah Hill.

Asylum seekers and other detainees have previously said they are terrified of the 501s, who have brought with them hardened prison attitudes, where guards are viewed as "dogs".

The union representing the guards, United Voice, previously warned mixing the 501s and asylum seekers was a dangerous mistake and the centre was a "pressure cooker".

The facility was originally set up to house single adult male asylum seekers in 2012.