The relatives of 16 of Harold Shipman's victims have contacted police in connection with jewellery worth about £10,000 that was found in his garage.
Shipman killed an estimated 250 people between 1971 and 1998
Greater Manchester Police (GMP) wrote to at least 180 of the families of the former Hyde GP's victims, asking them if they could identify the jewellery.
Items that the Shipman family could prove belonged to them have already been returned, police said on Thursday.
GMP will be meeting with the 16 victims' families "in the near future".
Solicitors acting on behalf of Shipman's widow, Primrose, have asked for all the items to be given back to her.
The solicitors - Pannone and Partners - have declined to comment on the issue.
Items that cannot be identified will be returned to Primrose
Greater Manchester Police said the collection of rings, brooches, earrings, bracelets and necklaces were of "varying estimated values".
The force said on Thursday it had an "unsubstantiated belief" that some of the jewellery was stolen from Shipman's victims.
Police asked the victims' families to provide a receipt, photographic evidence or a detailed description of the item before 15 April.
The official inquiry into the serial killer's crimes found he killed an estimated 250 people during his time as a doctor in Hyde, Greater Manchester and Pontefract and Todmorden, West Yorkshire, between 1971 and 1998.