BERLIN -- German authorities are investigating a "presumed terrorist attack" after a large truck plowed through a crowd at a Christmas market on Monday night in the heart of the capital, Berlin, killing at least 12 people and injuring dozens.
Berlin police that the truck "was steered deliberately into the crowd." It was carrying 25 tons of steel at the time, the vehicle's owner said.
"All police measures to the presumed terrorist attack at #Breitscheidplatz are running at full steam and all necessary precautions are taken," police said in a Twitter post on Tuesday morning.
Police are investigating the incident as a likely terrorist attack. The case has been handed to German federal police and public prosecutor.
A man believed to be truck's driver is being treated as a suspect. A second man found dead in the truck was Polish, not at the wheel when the crash occurred.
At least 48 people hospitalized when the truck hit the crowd. Victims have yet to be formally identified and no names of the victims have been released.
The attack "does not only hit Berlin right into its heart, it hits all of us," Germany's Justice Ministry said in a statement on Tuesday.
German Cancellor Angela Merkel's spokesman Steffen Seibert tweeted: "We are mourning the dead and hope that there is help for the many wounded."
Driven from Poland
The truck that devastated the Breitscheidplatz market is owned by a Polish company and appears to have been driven across the border for the attack.
Ariel Zurawski, owner of the truck company, said it may have been hijacked as his cousin -- the truck's regular driver -- couldn't have been behind the wheel. It was being used to transport steel.
"My scenario is that they did something to him and hijacked this truck," Zurawski told TVN 24.
He said that his cousin's wife had attempted to phone him multiple times but was unable to get through. The German capital is around a 90-minute drive from the Polish border.
Berlin police said a man found dead in the truck after the accident was a Polish citizen. He was not at the wheel during the incident.
Police said another man, apparently the driver, was picked up just over a mile from the scene and is being treated as a suspect.
'It felt like slow motion'
At Breitscheidplatz on Monday evening, it was a quintessential German Christmas scene: Trees strung with lights, vendors serving candied fruit and waffles, the smell of gluhwein -- German mulled wine -- wafting through the cold December air.
Shoppers were milling around buying snacks and gifts in the final days before the holiday at the colorful market, set up at the foot of an old church.
American Shandana Durrani was at the market and had stopped to reply to a text message when the truck rammed into the crowd at around 8 p.m.
She was lucky to have stopped, she said, as the truck mounted the curb, mowing people and stalls down just 20 feet in front of her, sending the crowd "running, scurrying, screaming."
"I heard some popping and thought maybe there was a guy with a gun," she said. "People just started running and dropping their gluhwein."
She said that the it looked as if the driver had just mounted the curb and lost control, and that the whole thing probably lasted a mere 10 seconds.
"It probably didn't last very long, but it felt like it was in slow motion (as I ) tried to get away from it."
With German officials and the White House suggesting the crash might have been an act of terror, comparisons have been drawn with the attack in Nice, France in July.
In that incident, a truck rammed into a crowd gathered to see Bastille Day fireworks, killing 86 and injuring more than 200 people.
Terror groups including ISIS and a branch of al-Qaida have encouraged their followers to use vehicles to stage attacks.
Before Monday's attack, the U.S. and U.K. governments had warned their citizens of potential security threats in Germany.
"There is a high threat from terrorism," according to U.K. foreign travel advice. "Attacks could be indiscriminate, including in public places visited by foreigners."
The U.S. had issued a blanket travel warning for Europe, saying there was "credible information (which) indicates terrorist groups continue plotting possible attacks."