A convicted child killer, responsible for one of Queensland's most horrific murders, is clinging to life after being found unresponsive in his jail cell.

Rick Thorburn was sentenced to life in prison after pleading guilty to murdering 12-year-old foster daughter Tiahleigh Palmer.

Tiahleigh was last seen at her school south of Brisbane in October 2015.

Yesterday, just two years into his 20-year sentence, Thorburn was found unconscious in his cell at Wolston Prison.

A Queensland Corrective Services spokeswoman said Thorburn was found unresponsive in his single occupancy cell at morning unlock.

He was taken to the Princess Alexandra Hospital in a critical condition.

Authorities have had previous concerns of self-harm with Thorburn.

"Queensland Corrective Services can confirm that a prisoner was transported by QAS to the Princess Alexandra Hospital after being found unresponsive in their single occupancy cell at Wolston Correctional Centre at unlock yesterday morning," a QCS spokeswoman said.

"The prisoner remains in hospital at this time."

Thorburn is currently in "critical but stable condition" in the Intensive Care Unit at the PA hospital, a hospital spokeswoman said.

Originally published as Tiahleigh's killer found 'unresponsive' in cell