The Swiss armaments company, Oerlikon Contraves Pyrotec, says its controversial tests with depleted uranium weapons in the 1960s involved a maximum of 133 shells.

The tests were carried out in Zurich, Geneva and at a testing ground at Ochsenboden in central Switzerland.

In a statement released on Thursday, the company said an internal investigation launched in the wake of Europe-wide fears about the health risks of the weapons had found the limited tests were carried out between 1966 and 1969.

Oerlikon said just under half of the shells were tested at its outdoor site in Ochsenboden (10 in 1966 and another 52 in 1968), while the remainder were tested at indoor sites in Zurich and Geneva.

The company said the shells each contained between 40 and 75 grammes of depleted uranium, and that the waste was treated as hazardous material.

A detailed report on the findings, based on the company's records and interviews with staff involved in the experiments, has been handed over to the authorities.

The company said that none of its staff who later contracted cancer had taken part in the tests.

Several countries, including Switzerland, Italy and Germany, have called for a moratorium on the use of depleted uranium weapons until research shows whether the radioactive material is responsible for a spate of cancers in soldiers.

There has been an unusually high rate of cancers, notably leukaemia, in troops who served in Bosnia-Herzegovina and Kosovo, where Nato used depleted uranium weapons extensively.

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