Body parts and tissue from soldiers killed in Afghanistan have been kept without permission from their families, the Ministry of Defence has said.
About six body parts and more than 50 tissue samples were found when a new manager was appointed at the Military Police's Special Investigations Branch.
An Army spokesman said there had been "a small number of cases" where procedure had not been followed.
The SIB is now trying to identify families affected as soon as possible.
The body parts were found at the John Radcliffe Hospital, in Oxford, while the tissue samples were discovered at the SIB at Bulford Garrison.
The discovery was made last month.
The number of families affected is likely to be less than 60 because multiple samples were taken for each case.
The tissue samples were kept on laboratory slides for matching or identifying the soldiers killed.
"There are occasions when it is necessary for the RMP Special Investigations Branch to retain slides of forensic material from individuals killed on operations as part of their investigation - this is standard practice," the spokesman said.
"However, the RMP identified there were a small number of cases where this had been done without the correct processes being followed to inform families."
Investigations into the matter were being carried out urgently, the spokesman added.
The MoD is blaming the mistakes on a change in the way the SIB liaised with families.
Procedures were subsequently changed again as soon as the discovery came to light last month.