A truck rammed into a crowded Christmas market in Berlin Monday night, killing at least 12 people and injured 48 others in what witnesses described as a deliberate attack.

German authorities said they are still investigating whether the crash was an accident, but a statement from the White House National Security Council (NSC) said the incident "appears to have been a terrorist attack."

The large Scania truck with a Polish license plate crashed into the market outside the Kaiser Wilhelm Memorial Church. The truck came to a halt on a sidewalk on one side of the market, shortly after ramming a large stand called "Fascination Christmas," ripping off one side and knocking down a large Christmas tree. The three-meter tree lay in the street, red and gold ornamental balls still attached to its limbs and a golden star at the top.

Police said a suspect believed to be the driver was arrested about 1 1/2 miles away, near Berlin's Victory Column monument. A passenger in the truck died at the scene as paramedics were attending to him.

Authorities initially estimated that 50 people were injured. Police later revised the total to 48, while Berlin's fire brigade said others were "more mentally injured."

Germany christmas market attack

Police stand beside a damaged truck which ran into crowded Christmas market in Berliin Berlin, Germany, Monday, Dec. 19, 2016. (AP Photo/Michael Sohn) (Copyright 2016 The Associated Press. All rights reserved.)

The Polish owner of the truck said he feared the vehicle, driven by his cousin, may have been hijacked. Ariel Zurawski said he last spoke with the driver around noon, and the driver told him he was in Berlin and scheduled to unload Tuesday morning.

"They must have done something to my driver," he told TVN24. Zurawski added that the truck had been loaded with steel structures weighing 25 tons.

Die Welt newspaper reported that the arrested suspect is a Pakistani known to police for minor criminal offenses, but not terrorism. The newspaper also reported that the dead passenger was a Polish national.

There was no immediate claim of responsibility, but the incident had a chilling echo of the July 14 truck attack in Nice, France that killed 86 people.

ISIS claimed responsibility for the Nice attack, which was carried out by a Tunisian living in France. ISIS and Al Qaeda have both called on followers to use trucks in particular to attack public places.

Mike Fox, a tourist from Birmingham, England, told The Associated Press at the scene in Berlin that the large truck missed him by about three yards as it drove into the market, tearing through tables and wooden stands.

"It was definitely deliberate," Fox said. Fox said he helped people who appeared to have broken limbs, and that others were trapped under Christmas stands.

Dozens of ambulances lined the streets waiting to evacuate people, and heavily armed police patrolled the area. Police on Twitter urged people to stay away from the area, saying they needed to keep the streets clear for the rescue vehicles.

Federal prosecutors, who handle terrorism cases, took over the investigation, according to German Justice Minister Heiko Maas. But Berlin's top security official, state interior minister Andreas Geisel, told RBB television that it was too early to say whether it was an attack, and called reports that the truck may have been hijacked "pure speculation."

Even so, some politicians were pointing fingers. Marcus Pretzell, a prominent member of the anti-migration Alternative for Germany party, lashed out at the government of Chancellor Angela Merkel, saying on Twitter: "When will the German state of law strike back? When will this cursed hypocrisy finally stop? These are Merkel's dead! (hash)Nice (hash)Berlin."

U.S. President-elect Donald Trump issued a statement calling the attack "horrifying."

"Innocent civilians were murdered in the streets as they prepared to celebrate the Christmas holiday," Trump said. "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."

Germany has not experienced any mass-casualty attacks by Islamic extremists, but has been increasingly wary since two attacks by asylum-seekers in the summer that were claimed by ISIS group. Five people were wounded in an ax rampage on a train near Wuerzburg and 15 in a bombing outside a bar in Ansbach. Both attackers were killed.

Those attacks, and two others unrelated to Islamic extremism in the same weeklong period, helped stoke tensions in Germany over the arrival last year of 890,000 migrants.

Monday's incident comes less than a month after the State Department warned U.S. citizens to be cautious in markets and other public places, saying extremist groups were focusing "on the upcoming holiday season and associated events."

In a statement, State Department spokesman John Kirby condemned the "horrendous events" at the Christmas market.

NSC spokesman Ned Price said the United States has already been in contact with German officials and stands ready to assist in the investigation and response.

Law enforcement sources tell Fox News that the FBI's Legal Attache (LEGAT) office in Berlin had been in touch with German officials to offer intelligence support to investigators. The sources said late Monday that no Americans had been identified among the victims.

Zurich police search for gunman after shooting at mosque; at least 3 injured

Last week, German prosecutors said a 12-year-old boy attempted to set off a nail bomb at a Christmas market in the southern city of Ludwigshafen.

The German-born son of Iraqi parents is alleged to have tried to set off the device at the Christmas market on Nov. 26, and again outside city hall on Dec. 5, Focus magazine reported, citing security sources.

In the second failed attempt, a passer-by spotted the backpack containing the device and reported it to authorities. Inside they found a glass jar packed with firecrackers with nails taped to it, Focus reported.

Police said it would have burned but would not have exploded.

Fox News' Matt Dean and The Associated Press contributed to this report.