According to staff reports, shots were fired during the break out.
"A rope appeared over the fence and into the exercise yard where there were two members of staff. I don't know at this point exactly how many inmates there were. When one of them climbed up the rope an employee tried to stop him, but then a person appeared on the fence with a pistol-like object. The staff member then let go and ran away and thought he heard shots," said Jürgen Büttner at the centre.
"The staff are feeling okay under the circumstances," he said to news agency TT later in the evening.
Inmates at the detention centre are offered the chance to exercise twice a day, for a total of three hours. Escapes have happened, but never with weapons involved.
The centre is located in the Södertull area of the city and all of those held there have been issued with a deportation order.
"It is very probable that this is the reason behind the escape," said Büttner.
Witnesses reported seeing the inmate and the gang run several hundred metres to a waiting car, according to Peter Hultqvist at the local police.
Police investigators are continuing their examination of the location on Monday.
"Most indications are that the shots were not live rounds," said Hultqvist.