A teenager suspected of attacking 28 people with a knife in a rampage in the German capital has denied being involved, officials said Saturday, despite dozens of witness statements and the seizure of the weapon.

The 16-year-old student from Berlin is under investigation for attempted murder after he was apprehended late Friday at the scene in Berlin's government district.

Police said the youth, whose name has not been released, had told them he had been drinking heavily during the celebrations and could "remember little" about what happened next.

"We're in the dark about the possible motive," said Gerd Neubeck, the city's deputy police chief. "He denies being the one that caused these injuries."

The youth is suspected of stabbing and hitting dozens of people in just ten minutes as he mingled with thousands of people heading home after a light-show to celebrate the opening of Berlin's new central railway station.

Fifteen of the 28 adults injured needed hospital treatment, including several whose lives were saved by emergency surgery after rescue teams swarmed to the area near the Reichstag parliament building. Police said there were no foreigners among the victims.

Police urged the victims to take a HIV test after one of those stabbed said he was HIV-positive. The disease can be transmitted in contaminated blood.

Detective Klaus Ruckschnat said investigators had seized the knife they think was used in the attack and were still questioning about 60 witnesses about what happened. He said several had identified the suspect.

The youth, identified only as a German high school student from the city's working-class Neukoelln district, was known to authorities for once fighting with a co-student and for breaking a school window.

But they said there was nothing in that record or in his family background to explain his alleged actions.

The attack comes amid a rash of hate crimes in Germany, including several in Berlin, that have raised concern about security two weeks before the country hosts the soccer World Cup.

Berlin's state interior minister insisted that Friday's attacks were the freak act of an individual and shouldn't sour the city's image before the soccer tournament begins next month.

"These things happen in the United States, they happen in Germany," Erhard Koerting said. "When people look to Berlin and the World Cup, they won't think of a place where people run amok but as an exciting city where, as in other cities, there are sometimes terrible crimes," he said.