German authorities have released a man who was arrested after they found his number on the phone of Berlin truck attacker Anis Amri.
The 40-year-old, a Tunisian, was taken into custody after officers searched his home and workplace.
Prosecutors had been focusing on a mobile phone voice message and a picture sent by Amri to a contact shortly before the attack – but have now determined that contact was not the man who was arrested.
Spokeswoman Frauke Koehler said: “The investigation into further accomplices or possible people who knew… will continue at full speed.”
She also confirmed the truck that ploughed into the market was only stopped thanks to an automatic braking system that activates when impacts are detected.
Meanwhile, Italian police have searched three homes in and around Rome where Amri may have spent time, judicial sources told Reuters.
Amri was shot dead after opening fire at Italian police officers four days after the attack on a Christmas market in the German capital, in which 12 people died.
The attack has forced police forces across Europe, including those in the UK, to reassess their security needs for New Year’s Eve.
His fingerprints and wallet were found in the truck.
German prosecutors have now said that the weapon he used in Italy had the same calibre as the one he had used to hijack the truck used in the Berlin attack – whose driver was shot dead.
Investigators have been trying to piece together how Amri got from Berlin to Italy after the attack.
His route appears to have taken him to Nijmegen in the Netherlands and via a bus to Lyon in central France.
Amri was picked up on CCTV at a railway station there before travelling to Chambery.
His precise movements after that are unclear. Sky News has been told he was seen in the French mountain resort town of Chamonix.
He is also understood to have taken a train on to Milan, where he was killed in a shoot-out with police.
His journey across Europe has prompted fears that open borders in Europe’s Schengen zone are being exploited by Islamic State.
Amri, who pledged allegiance to IS in a video, had first arrived in Europe after taking a boat to the Italian island of Lampedusa in 2011.
Searches by Italian authorities have focused on Rome and nearby Acilia, where he is thought to have stayed after leaving a detention centre in Sicily in 2015.
Italian prime minister Paolo Gentiloni told a news conference on Thursday that Amri was probably radicalised after arriving in Europe.
But he said the government had no evidence that he had “particular networks” in Italy.