The Swiss defence ministry has confirmed that ammunition containing depleted uranium was tested in Switzerland during the 1970s. What happened to the spent shells, however, remains unclear.
The defence ministry spokesman, Oswald Sigg, said details of the tests, carried out by the Oerlikon-Bührle subsidiary, Contraves, emerged last week.
Sigg said the ministry is seeking information on the conditions in which the tests were held, who gave permission for them, and where the spent ammunition was stored or destroyed.
The tests were carried out at an army training ground at Unteriberg in the central canton of Schwyz.
The cantonal authorities have now called for samples from the area to be taken and analysed by the radiation laboratory in Spiez.
According to newspaper reports, the training area was converted into a golf course last year. The "SonntagsBlick" newspaper reported that the area was not tested for radiation particles because the danger of uranium-tipped ammunition was not previously known.
The dangers have come to the fore in the past few weeks after disclosures that several soliders who served in Balkans peacekeeping operations in the 1990s contracted leukaemia and died.
Most of the victims have been Italians, but the death of a Swiss soldier from leukaemia in 1998, after serving in Bosnia-Herzegovina, is now being re-assessed.
The Swiss defence ministry confirmed on Friday it was aware that Nato weapons contained depleted uranium before it sent its troops to help peacekeeping operations in Kosovo.
However, the head of the Swiss contingent, Christoph Brun, said that soldiers, who respected the regulations concerning the handling of mines and munitions, "could not have come into contact with depleted uranium".
Swiss soldiers serving in the Balkans were instructed not to touch or take home weaponry. However, many Swiss soldiers have admitted to collecting weapons as souvenirs.
Last week, the Swiss army ordered medical check-ups for all troops who served in the Balkans and began collecting any arms taken home by Swiss troops.
swissinfo with agencies