Authorities are detaining a 40-year old Tunisian believed to information regarding the Berlin attack in a busy Christmas market that killed 12 people and injured dozens of others.

German state prosecutors, according to the BBC, said that police raided the workplace and residence of the suspect in Tempelhof, Berlin after investigators found his number on the cell phone of Berlin attacker Anis Amri.

The police are yet to issue a statement regarding his possible involvement in the incident and have until Thursday to decide whether to formally arrest the man or not. The person's identity was not disclosed.

Police also found a Dutch Sim card inside the backpack of Amri after his death, which may have been handed over to him by an unidentified person in a train station in Nijmegen, The Netherlands. An image of Amri was caught by a CCTV camera in the station after the attack.

Berlin attacker Amri was killed in a shootout with police near a train station in Milan days after the truck attack when he shot at police officers conducting a routine. Investigators claim that the suspect commandeered a lorry loaded with steel and shot the truck driver to take control of the vehicle and rammed it into a busy holiday market.

The truck driver, Lukasz Urban, was fatally shot in the head in what police believed may have been caused when Urban was taken hostage by Amri where there may have been a struggle before he was shot. Doctors also believe that Urban was shot hours before the Berlin truck attack.

Investigators also reveal that the attack could have claimed more lives were it not for the automatic brake system of the truck that kicks in as it senses a crash impact. This may have prevented Amri from further crashing through to more people in the marketplace.

Amri fled the scene of the attack and was able to travel through two European borders before he was eventually killed in the shootout. Amri was believed to have been recruited into the ISIS militant group and was believed to have been sworn in based on a video posted online after the Berlin attacks.

The Berlin attacker's full name is Anis Ben-Mustafa Ben-Outhman Amri who hailed from Tataouine, Tunisia. The 24- year old was believed to have left his home back in 2011 for Italy. Acquaintances say he is a socially conservative person.

Amri was also linked with Islam preacher Ahmad Abdelazziz alias Abu Walaa, who was arrested in November for plotting terror attacks in Germany.