The fire, which police suspect was deliberately lit by a detainee, broke out Wednesday night in a temporary housing section of the prison where nearly 40 people were being held awaiting deportation.
The Moroccans, aged 31 and 32, were severely burnt and remained in comas Thursday, though a police spokesman said their lives were no longer in danger.
One other prisoner and seven staff were taken to hospital suffering mild smoke inhalation.
TV weatherman Jörg Kachelmann, who is awaiting charges of raping his girlfriend, is being held at the same prison.
Police were investigating the cause of the fire on Thursday. A spokesman has said investigators had spoken to a witness – one of the detainees – who said another prisoner had deliberately lit the fire.
The incident, which also caused tens of thousands of euros damage, has echoes of the death in a police station cell fire six years ago of asylum seeker Ouri Jallow, which sparked controversy and protests.