The German authorities released a 40-year-old Tunisian man on Thursday who had been detained a day earlier as a possible accomplice in the truck attack on a Berlin Christmas market, a spokeswoman for the public prosecutor general said.
The man, whose name has not been made public, was held on Wednesday after police officers searched a home and offices in Berlin as they hunted for someone with whom the driver of the truck, Anis Amri, may have communicated by text and video before the attack, the spokeswoman, Frauke Köhler, said.
“Further investigation showed, however, that the man who was temporarily detained was not the possible contact person of Anis Amri,” Ms. Köhler said, “and so he had to be released again.”
She confirmed that the authorities who examined unspecified videos now believe that Mr. Amri, 24, fled Germany via the Netherlands, France and Italy. He was shot and killed early Friday morning after drawing a gun and wounding one of the two police officers who stopped him during a routine identity check in a Milan suburb.
Mr. Amri, who left Tunisia in 2011 and served time in six jails in Italy before arriving in Germany in July 2015, has been identified as the driver of a tractor-trailer that careened into the market on the evening of Dec. 19, killing 12 people.
Investigators have since established that he used at least eight aliases and was registered at several offices for foreigners’ affairs, mostly in Berlin and North Rhine-Westphalia, Germany’s most populous state, according to news reports.
Ms. Köhler said the death toll would have been higher, were it not for an automatic braking system that kicked in shortly after the vehicle jumped the sidewalk. Mr. Amri apparently hijacked the truck from its Polish driver at a truck lot in Berlin.
“That prevented still worse results,” she said.
Under European Union rules, heavy tractor-trailers must be equipped with an automatic braking system, which can be overridden by the driver, although Mr. Amri did not do so. The police have said the truck came to a stop about 260 feet into the Christmas market, after hitting it at an estimated speed of 35 to 40 miles an hour.
The Polish driver was found shot and killed in the cab of the truck. Images of a bullet recovered from the truck have been sent to the Italian police, Ms. Köhler said, to see if it matches the bullet Mr. Amri fired at the officers near Milan.
A full autopsy report on the Polish driver will not be completed until the middle of next month, Ms. Köhler said, adding that the body showed no signs of stab wounds, as had been reported earlier by the news media.