BERLIN — A 40-year-old Tunisian man has been detained as a possible accomplice of Anis Amri, the man identified as the terrorist who carried out the truck attack on a Berlin Christmas market that killed 12 people, German officials said on Wednesday.
The detention occurred after a search of a home and offices associated with the man, whose name was not released. Information about him was found in the cellphone of Mr. Amri, a 24-year-old Tunisian, who was killed on Friday during a shootout with police officers outside Milan.
The development on Wednesday was announced by the office of Peter Frank, the public prosecutor general, which is based in Karlsruhe.
“Further investigations indicated that he could have been involved in the attack,” Mr. Frank’s office said in a statement, adding that officials expected to know by late Thursday if there were enough grounds to press criminal charges. “To what extent suspicions about the arrested person will be firmed up remains to be seen, after further investigation.”
The truck attack, on Dec. 19, was Germany’s most deadly terrorist attack in decades. The Islamic State claimed responsibility and released a video that Mr. Amri had recorded, in which he pledged his allegiance to the group’s supreme leader.
Italian and French officials have said that Mr. Amri most likely traveled by train on the evening of Dec. 22 from Lyon, France, transferring trains at the town of Chambéry, near the border with Italy, before making his way to Turin and then Milan. From Central Station in Milan, he went to the northern suburb of Sesto San Giovanni, where two police officers on a routine patrol stopped him early Friday morning and asked for identification; Mr. Amri opened fire and was fatally shot.
How Mr. Amri reached Lyon from Berlin remains unclear, but Agence France-Presse, citing unidentified Dutch officials, reported on Wednesday that he took a bus from Amsterdam or the Dutch city of Nijmegen to Lyon on Dec. 21, two days after the attack. (There is no direct bus service to Lyon from Amsterdam or Nijmegen; travelers have to changes buses in Brussels; Düsseldorf, Germany; Frankfurt; or Paris.)
“There are indications that he did travel via the Netherlands,” Wim de Bruin, a spokesman for the Dutch national prosecutor’s office, said in a statement on Wednesday. He did not to provide further details on how and from where Mr. Amri might have traveled in the Netherlands.
The authorities in Tunisia have detained for questioning several people who knew Mr. Amri, but there is no indication so far that they were aware of or involved in the attack.