Police charged Steven Freeman, 24, on Monday in relation to series of alleged police pursuits and car thefts in NSW and the ACT.

The Belconnen man faced the ACT Magistrates Court on Tuesday and was remanded in custody.

ACT Corrections Minister Shane Rattenbury confirmed police were investigating after an injured detainee was found in the Hume prison later that night.

"[Corrective Services] staff responded quickly to provide medical assistance and an ambulance arrived on the scene shortly after.

"The detainee was then transported to The Canberra Hospital in a critical condition."

Mr Rattenbury declined to comment further on the incident and said the matter had been handed to police.

ACT Policing said their investigations were ongoing.

An ACT Health spokesman confirmed Mr Freeman's condition remained critical on Wednesday night.

It is understood officers locked down the prison block, which holds about 40 prisoners, where Mr Freeman was found.

Four detectives were at the jail carrying out investigations into the incident on Wednesday.