German authorities scoured the country Wednesday for a Tunisian asylum seeker who is being sought in the truck rampage through a Christmas festival here that killed 12 people and injured 48.
Investigators don't know if there is more than one perpetrator at large. The new suspect emerged after police found documents in the truck belonging to a 24-year-old Tunisian national identified only as Anis A, the German magazine Spiegel reported on its website.
He was identified from a document relating to asylum that was found in the vehicle's cabin, Spiegel and Allgemeine Zeitung reported. The document said Anis A. was born in the southern Tunisian city of Tataouine in 1992, Spiegel said. It reported that he is also known by two aliases.
Sueddeutsche Zeitung reported that he applied for asylum in April and received a temporary residence permit.
Photographs purporting to be of Anis A. were circulating on social media.
A previous suspect, a 23-year-old Pakistani asylum seeker, was released Tuesday evening because prosecutors did not find enough evidence linking him to the incident. He denied any involvement in the assault.
Germany is treating the attack as terrorism, which the Islamic State said was carried out by a "soldier." No evidence has emerged establishing a connection to the militant group, which has staged and inspired assaults across Europe and the United States.
Berlin police urged people to be especially alert Wednesday and warned that the person or persons responsible were likely armed and dangerous. As of Tuesday night, police had received more than 500 tips about the attack. Security has been tightened in Berlin and across other European capital cities.
"I am relatively confident that we will perhaps tomorrow or in the near future be able to present a new suspect," Andre Schulz, the chairman of the Federation of German Detectives, told state broadcaster ZDF on Tuesday evening.
One report, by Berlin's RBB news, said the truck's driver may be injured and that police were using DNA recovered from the vehicle to see if the attacker was hiding among the injured in the hospital. A related theory circulating in German media is that the truck's original Polish driver, who was found dead at the scene, may have tried to fight the perpetrator and wrestle him for the steering wheel as the truck was being driven into the market. Police have not commented on that idea.
Six of the dead have been identified as German nationals, according to German news agency DPA, citing police. Another five have not yet been identified. The Polish driver was found dead in the truck's passenger seat. A woman from Italy and another from Israel were missing after the attack, according to DPA.
"We will not let cosmopolitan Berlin be taken by such a cowardly attack, by fear and terror," Berlin Mayor Michael Müller said at a memorial service at the Kaiser Wilhelm Memorial Church, close to the site of the attack, on Tuesday evening.
The prospect that the perpetrator is a recent migrant is fueling an anti-immigrant backlash in Germany, which has admitted nearly 1 million people fleeing conflicts in the Middle East and Africa under Chancellor
Angela Merkel’s liberal migration policy.