TOBIAS SCHWARZ/AFP/Getty Images(BERLIN) — The man detained after a Christmas market attack that killed 12 people in Berlin was released from custody Tuesday because of insufficient evidence, the federal prosecutor said, increasing the likelihood that other suspects may still be at large.

The man, who has not been publicly named, had a pending asylum case and first entered Germany on Dec. 31, 2015, the country’s interior minister said earlier Tuesday.

He arrived in Berlin in February and was not on any terrorist watch list, authorities said. He had denied involvement in the attack, according to Berlin police.

German and international officials have labeled the incident a terrorist attack, and the release of the man means authorities do not have any suspect in custody.

Shortly after announcing that someone had been taken into custody in connection with the attack, officials showed increasingly less confidence that he was involved in the attack.

Attorney General Peter Frank had told reporters earlier that officials should prepare for the possibility that the man they apprehended was not the person who plowed a truck into a crowd of people and that authorities were unsure whether multiple suspects are involved.

Now, not only is the attacker apparently at large, it’s also unclear how the terror incident was planned or whether the attacker had logistical support from anyone affiliated with terrorist organizations.

The truck involved in the incident was stolen in Poland from a building site, the Berlin police tweeted.

The use of a stolen truck as a weapon bears similarities to the July attack in Nice, France, when Mohamed Lahouaiej Bouhlel killed 86 people, including children, by driving a rented truck into a crowd of Bastille Day revelers.

The Tunisian-born Bouhlel was living in France. In December, French police detained 11 people suspected of providing logistical support in his attack.

German Chancellor Angela Merkel gave a brief statement Tuesday, saying, “This is a difficult day. I am, like millions of people during these hours, horrified and shocked by what happened at the Breitscheidplatz in Berlin.”

Flags flew at half-staff across Germany Tuesday as the country mourned the victims. Christmas markets in Berlin closed for the day, and the attorney general announced the beginnings of a criminal investigation.

A male passenger in the truck died at the scene, authorities said, and is being counted among the 12 fatalities.

“The man who was found dead in the truck did not control the truck that drove to the Christmas market,” Berlin police said early Tuesday, after earlier tweeting that the man was a Polish citizen.

White House National Security Council spokesman Ned Price described the incident as an apparent “terrorist attack.”

“The United States condemns in the strongest terms what appears to have been a terrorist attack on a Christmas market in Berlin, Germany, which has killed and wounded dozens. We send our thoughts and prayers to the families and loved ones of those killed, just as we wish a speedy recovery to all of those wounded. We also extend our heartfelt condolences to the people and government of Germany,” the statement reads.

Price added that the United States has offered to aid Germany in the investigation.

“We have been in touch with German officials, and we stand ready to provide assistance as they recover from and investigate this horrific incident. Germany is one of our closest partners and strongest allies, and we stand together with Berlin in the fight against all those who target our way of life and threaten our societies,” he said.

President-elect Donald Trump released a statement about the incident, saying, “Our hearts and prayers are with the loved ones of the victims of today’s horrifying terror attack in Berlin. Innocent civilians were murdered in the streets as they prepared to celebrate the Christmas holiday.”

He went on to appear to tie the incident to ISIS.

“ISIS and other Islamist terrorists continually slaughter Christians in their communities and places of worship as part of their global jihad. These terrorists and their regional and worldwide networks must be eradicated from the face of the earth, a mission we will carry out with all freedom-loving partners,” he said.

Copyright © 2016, ABC Radio. All rights reserved.