Prosecutors in western Germany have revealed they opened a fraud investigation earlier this year against Anis Amri, the main suspect in the Berlin Christmas market truck attack.
Officials suspected that he was simultaneously claiming benefits in two towns under different identities.
Detlef Nowotsch, a spokesman for prosecutors in Duisburg, said the investigation was opened in April but shelved in November because Amri's whereabouts were unknown.
Amri was accused of receiving asylum-seeker benefits in both Emmerich and Oberhausen for a few days in late 2015.
He is believed to have driven the truck that ploughed into a Christmas market in the German capital on December 19, killing 12 people. His fingerprints and wallet were found in the truck.
The Tunisian arrived in Germany in July 2015. Authorities later put him on a list of potentially violent Islamic extremists.
Amri was killed in a shoot-out with Italian police in Milan on December 23.