The Ministry of Defence has apologised after it emerged body parts and tissue thought to be from 30 soldiers killed in Iraq and Afghanistan were kept without permission from their families.
The MoD said it would confirm their identities on Thursday and would write to families offering a formal apology and details of the material held.
"A small number of cases" did not follow procedure, the MoD said.
Maj Gen James Everard said two families had already been informed.
He said one of the samples dated back to 2002.