Dounreay has revealed that post mortem samples of two deceased employees were sent to its Oxfordshire headquarters.
Dounreay was an experimental reactor facility
Analysis for radioactivity was permitted at the Harwell plant.
The cases will now be included in a major government inquiry into whether proper consent was sought from relatives.
The inquiry was widened after concerns that tissue samples could have been removed from 65 deceased employees, most of whom were based at Sellafield.
The UK Atomic Energy Authority (UKAEA) has confirmed that the Harwell cases include samples from two Dounreay employees who worked at the Caithness Plant between 1962 and 1991.
The records of former Dounreay workers are being checked as part of the inquiry into the removal of tissue from nuclear staff without consent.
UKAEA is working with Michael Redfern, QC, who is leading the investigation.
The inquiry was sparked by claims that samples were taken from former Sellafield employees who died in the 1960s.
Trade and Industry Secretary Alistair Darling announced that the inquiry would be extended to other sites.
UKAEA said there were indications that Harwell also participated in work related to deceased persons who were not employees of the nuclear industry.
Dr John Crofts, UKAEA director of assurance, said: "Our priority now is to complete a thorough search and review of our records and to ensure that all relevant information is made available to Michael Redfern QC.
"For the benefit of everyone involved, especially any affected families, we will complete this review as sensitively and speedily as possible."
British Energy said the inquiry did not involve its sites at Torness in East Lothian, or Hunterston B in Ayrshire.
Calls for an inquiry were made last week by the GMB and Prospect unions.