Berlin Attack: Manhunt Continues, Police Say More Than One Suspect On The Run

German authorities are still searching for the driver of the truck that plowed into a central Berlin Christmas market Monday, killing at least 12 and injuring dozens.

In a striking development, police released the Pakistani suspect that they had detained in the aftermath of the attack because of a lack of evidence, Germany's chief federal prosecutor said Tuesday. Police had arrested 23-year-old Pakistani national Naved B. near the scene of the crash but he had denied any role in the attack.

A German counterterror source told Newsweek before the suspect's release Tuesday that he would be cleared of suspicion as he had no blood on him, despite an apparent struggle in the cab of the truck that left its original driver, 37-year-old Polish national Lukasz Urban, dead with stab and gunshot wounds. The federal prosecutor later confirmed that an examination of the truck's cab and the suspect revealed no evidence that he was present in the truck.

It confirmed fears that the perpetrator of the attack may still be at large.

"No-one will rest until the perpetrator or perpetrators have been caught," Interior Minister Thomas de Maiziere told German media, the BBC reported.

Authorities said they were not ruling out the possibility that more than one suspect could be involved in the attack. They said it remains unclear if the perpetrator was acting on his own or with others, Reuters reported. Holger Muench, head of Germany's federal police, told reporters at a press conference Tuesday, that the investigation is focusing on "whether there are other perpetrators that we need to arrest" as they did not "know whether there is only one" attacker. As the perpetrator could be armed, police have warned residents of the German capital to remain alert.

Berlin Mayor Michael Mueller ordered increased security in the city, with additional police stationed at sensitive sites and barriers placed at markets because of the threat of further attacks. Berlin's Christmas markets remained shut on Tuesday but the Interior Ministry said that events outside the capital would remain open, albeit under tight security.

"The right thing is to keep your eyes open—be vigilant in this situation. But you can move around safely in public places. There is no need for panic," he said.

The Islamic State militant group (ISIS) claimed the attack late Tuesday via its Amaq news agency. The group said one of its "soldiers" had carried out the attack, but did not name the attacker. The statement is difficult to verify as there is currently no suspect in the case but the group rarely issues a claim of responsibility while the main perpetrator is still alive.

German Chancellor Angela Merkel said Tuesday that they "must assume at the current time that it was a terrorist attack." The federal prosecutor said the driving force behind the attack was that of a radical Islamist group, as seen in the ISIS-claimed attack on the southern French city of Nice in July. But he said that no motive has been established.

Right-wing politicians in Germany were quick to link the attack to Merkel's open-door refugee policy in 2015 that allowed more than 1 million people to enter the country. Marcus Pretzell, a regional leader of the Alternative for Germany party, described the victims as "Merkel's dead." Frauke Petry, the party's leader, said: "Germany is no longer safe."

Merkel herself acknowledged that there was a possibility that an asylum seeker may have carried out the attack, although this remains unconfirmed. "I know that it would be particularly difficult for us all to bear if it turned out that the person who committed this act was someone who had sought protection and asylum in Germany," she said.

The truck rampage brings Germany into the group of European nations, such as France and Belgium, that have suffered mass casualty attacks claimed by ISIS in recent years.