The investigation is particularly sensitive because the prison was the site of a different attempted escape two weeks ago in which a prisoner managed to saw off his cell window's bars before hiding in a prison attic.
In this latest case, the 47-year-old awaiting extradition to Poland is said to have been cleaning part of the prison on Sunday morning when he broke through a seven-centimetre-thick bulletproof glass window and ran away. Police launched a manhunt using helicopters and dogs, so far without success.
“Errors of this sort can simply not occur,” said North Rhine-Westphalia Justice Minister Thomas Kutschaty who ordered an immediate inspection of windows at the state's 37 correctional facilities.
The escape could have political implications – the centre-right Christian Democratic Union (CDU) and pro-business Free Democrats (FDP) have asked for the situation to be discussed in the state parliament.
Among the issues to be clarified is why there was “information chaos” after the escape, said CDU representative Peter Biesenbach. The prison initially reported that the escaped prisoner was not violent, but this was later contradicted by the state Ministry of Justice.
North Rhine-Westphalia has had problems with prison security in the past, but officials have said that conditions improved after a modernisation in the mid-1990s.