“We’re trying to establish which mine it came from and how it came into the hands of the culprits,” said police spokesman Colonel Jay Naicker, who described the uranium as a raw mined product.
The two men, both in their early 20s, were arrested last week with the uranium and 90 ecstasy tablets.
They appeared in court on Monday charged with being in possession of the drugs and the kilo (about two pounds) of uranium.
The case has heightened fears over the illicit trade in enriched materials that could be used in dirty bombs.
“We would have to establish whether it’s just a small batch that they got their hands on or whether they’ve got access to more of the stuff,” Naicker said.
The South African Nuclear Energy Corporation (NECSA) confirmed that the substance was uranium and is testing its isotopic identity and levels.
“In order to produce a dirty bomb, one would have to obtain certain amounts of enrichment on the uranium,” Elliot Mulane, NECSA spokesman, told AFP.
“These tests will reveal the enrichment levels of the material, and with that revelation we will be able to confirm whether it can be used in a dirty bomb or in other clandestine or illegal activities.”
However, he said it was unlikely that highly enriched — that is, weapons-grade — material would have been sold on the street.
“Highly enriched uranium worldwide is stored in very, very high-security areas, and the chances that anyone could lay their hands on these materials are almost nil,” he said.
“So I’m not very concerned about highly enriched uranium ending up in the wrong places.”
Uranium trafficking is rare, with only five such cases in the past 20 years, Mulane said.
But he admitted that the theft was “a concern”, citing the issue of safeguards at mines and fears over the possible toxicity of the substance.
The material is likely to have come from a mine, possibly not within South Africa.
South Africa has the continent’s only nuclear power plant, but several countries have significant uranium deposits and mining activities.
The results of the tests on the uranium are expected Thursday.
International atomic bodies have been informed of the seizure.
The men were remanded in custody until December 3 for a bail application. – Sapa/AFP