In connection with the jewel theft from the Green Vault in Dresden, the police are looking for another possible suspect.
The previously unidentified man is said to have been in the jewel room for a long time and several times the day before the burglary in November 2019, police and prosecutors said.
His behavior deviated "conspicuously" from that of an average museum visitor.
The man may have spied on the premises and passed information on to the thieves.
The police and public prosecutor's office published images from surveillance cameras in the Green Vault on Wednesday.
Anyone with information about the suspect should contact investigators.
The trial against six suspects for serious gang theft and arson is currently underway at the Dresden Regional Court.
The men are said to have stolen jewelry worth 113 million euros during the burglary on November 25, 2019.
The investigators are convinced that the crime was committed by criminal members of a well-known Berlin clan.