Three people including the nephew of the Berlin Christmas market attacker Anis Amri have been arrested in Tunisia.
Tunisia's Interior Ministry said Amri - who was shot dead on Friday - had sent his 18-year-old nephew Fedi money to join him in Europe.
Twelve people were killed and dozens more injured in the attack on Monday.
A spokeswoman for the German federal prosecutor's office has confirmed investigators carried out multiple searches across Germany on Thursday.
She said no arrests have been made but forensic evidence gathered so far suggests the suspect, identified on Wednesday as 24-year-old Anis Amri, drove the truck used in the Christmas market attack.
The funeral for the lorry driver killed in the Berlin Christmas market attack has taken place in his home country of Poland.
Footage has emerged of the final moment before a truck ploughed into a crowd of people at a Christmas market in Berlin.
A man is being hunted by German police after a lorry ploughed into a Berlin Christmas market on Monday, killing 12, but who is the suspect?