German authorities on Tuesday released a Pakistani asylum-seeker suspected of driving a truck into a Berlin Christmas market and killing 12 people due to a lack of evidence and the interior minister said the real perpetrator may still be on the run.

The truck smashed into wooden huts serving mulled wine and sausages on Monday evening at the foot of the Kaiser Wilhelm memorial church, one of west Berlin’s most famous landmarks. Forty-five people were injured, 30 severely.

Islamic State claimed responsibility the attack, saying the perpetrator was a “soldier” of the militant group.

“He executed the operation in response to calls to target nationals of the coalition countries,” its AMAQ news agency said.