Updated

A special investigator appointed by the German state of Berlin says the Tunisian man who carried out last year's deadly truck attack on a Christmas market in Berlin could have been detained months earlier.

Anis Amri, a failed asylum-seeker, killed 12 people in the Dec. 19, 2016, attack that was later claimed by the Islamic State group. Public inquiries and German media have since uncovered a series of mistakes by security agencies in tracking a man who authorities believed had posed a public threat.

Bruno Jost, a former federal prosecutor, said Thursday that Amri could have been held for several months for alleged forgery and other crimes when he was detained in southern Germany on July 30, 2016. But Jost said no police agencies familiar with his case reacted to the arrest.