Six inmates of Capricornia Correctional Centre in central Queensland have been taken to hospital — with one of them airlifted — after a suspected mass drug overdose.

Queensland Corrective Services (QCS) has confirmed a number of prisoners had "fallen ill".

"Initial indications are that the symptoms may be related to drug ingestion, however we are working with Queensland Ambulance Service, Queensland Health and Queensland Police Service to establish the cause of the incident," a QCS spokesperson said.

"The prison has been placed into lockdown, and all prisoners are being closely monitored for signs of illness."

Six inmates at Capricornia Correctional Centre are thought to have overdosed on an unknown substance. ( ABC News: Jonathan Hair )

QCS also confirmed a prison officer had suffered a minor injury during the overdose incident.

It is understood the injured officer was assessed at the scene but has remained at work.

It is not clear at this stage what substance the inmates ingested.

Seven ambulance units attended the prison, with six inmates reported to be ill.

One inmate was flown to Rockhampton Hospital in a serious but stable condition.

Five others were transported to the hospital by road in a stable condition.

A Queensland Ambulance Service (QAS) spokesperson said they were called to the correctional centre at Etna Creek, north of Rockhampton, just before 1:00pm.