Berlin police have detained a 40-year-old man (his identity has not been released yet) after finding his phone number in Anis Amri‘s phone. Anis Amri killed 12 people and wounded 48 after he drove a semi-truck through a crowded Christmas market in Berlin on Dec. 19. Amri was eventually killed near Milan after he fired at Italian police.

According to the New York Times, the Tunisian man may be an accomplice to the Berlin attack. However, charges have not been filed against him yet.

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.””