There is growing concern that uranium - which could be used to make nuclear bombs - is being secretly mined and smuggled out of the Democratic Republic of Congo.
Inspectors from the IAEA are to visit the DRC in April
This week File on 4 investigates the claims ahead of a planned visit to the DRC by inspectors from the United Nations nuclear watchdog, the IAEA.
For more than a century, Congo's vast mineral wealth has been its curse. Over the past decade it has been plundered by rebels and warlords fighting a war in which four million people have died.
Officially, no uranium at all should now be leaving the country. But the United Nations has reported that in the past six years more than 50 cases of smuggled uranium have been seized in Congo.
And a report published last July by the UN left little doubt about who was to blame.
It said: "The frequency of the seized consignments in the central African region leaves no doubt that the extraction and smuggling of radioactive material must be the result of organised efforts, and that these illegal activities must be highly rewarding financially.
"It is equally clear that the Government of the Democratic Republic of Congo is at the very least tolerating these risks, since it makes neither any attempt to prevent access to the most important mining sites, nor does it credibly monitor the radioactivity of exported materials."
There is particular concern about a mine called Shinkolobwe. It is famous as the source of much of the uranium that was used for the Hiroshima and Nagasaki bombs.
Officially it closed decades ago. But unofficially it has continued to be worked by miners operating in hazardous conditions.
In November last year a UN mission visited the mine. Their report has not been published yet.
The new governor of Katanga, Moise Katumbe, insists that whatever happened in the past, things are different now.
"Today I'm the governor of the province. I will stop all those things, that's why I say the British and American are welcome to bring their people to check," he says.
Patricia Feeney, director of a campaigning organisation called Rights and Accountability in Development says action is overdue.
The worry is, who is buying in this nuclear black market. There are rumours it could be Iran or North Korea.
But there is also the terrifying prospect that this material could end up in the hands of terrorists.
Hear the full story on Radio 4: File on 4 Tue 27 Feb 2007 at 2000 GMT