The Islamic State group has claimed responsibility for the attack at a Berlin Christmas market on Tuesday, which killed at least 12 people and injured around 50 others. However it remains unclear whether the attacker was directly affiliated with the organisation. German officials said the perpetrator might still be at large, Deutsche Welle reported. The militant group, via its news agency Amaq, said the attack meant to “target citizens of the Crusader coalition”.

On Wednesday, German interior minister Thomas de Maiziere said the man arrested on the suspicion of involvement in the attack was a 23-year-old Pakistani national who had applied for asylum. Germany’s Chief Federal Prosecutor’s Office later issued a statement saying he had been released as “the investigation did not yield any urgent suspicion against the accused”.

The police said they may have arrested the wrong man and it is uncertain if the Pakistani national was really the driver. A Polish freight company owned the truck and its owner was found dead in the vehicle, Reuters reported.

Condoning the attack, German Chancellor Angela Merkel had said, “I know that it would be particularly difficult for all of us to bear if it is confirmed that this deed was carried out by a person who sought protection and asylum in Germany,” she was quoted as saying by The New York Times.

United States President-elect Donald Trump said Islamic terrorists were responsible for the attack, without mentioning any evidence. He said terrorists must be “eradicated from the face of the earth” and vowed to fulfil that goal with all “freedom-loving partners”, AP reported.