BERLIN - German federal prosecutors say they have searched properties in western Germany and in Berlin where truck attack suspect Anis Amri is believed to have spent time.

Prosecutors' spokeswoman Frauke Koehler told reporters there were searches at "various locations" in North Rhine-Westphalia state and in the capital on Thursday. Authorities also checked a bus in the southwestern German city of Heilbronn after receiving a tip. They haven't yet made any arrests.

Koehler said Amri's fingerprints have been found on the driver's door and on the side of the truck. She added: "We believe that Anis Amri was steering the truck."

Prosecutors issued a formal arrest warrant against Amri. That formality will enable them to hold him pending a possible indictment once he is arrested.