Two men accused of being part of a network to exploit the Democratic Republic of Congo's uranium have been released after their arrest last week.
Enriched uranium is used for nuclear power generation and weapons
Scientific Research Minister Sylvanus Mushi said they are still accused of belonging to the international ring.
He said as the nuclear officials had not informed their superiors about a deal they had made with a London-listed company to export uranium, it was void.
But Mr Mushi's predecessor said on Monday that the deal was legitimate.
Kamanda wa Kamanda said that if the deal was cancelled, it would open the door to illegal trading.
The dispute comes amid reports that a large quantity of uranium has gone missing in recent years in DR Congo.
DR Congo's top nuclear official Fortunat Lumu and his colleague were released after being held in custody for three days.
The BBC's Arnaud Zajtman in the capital, Kinshasa, says they were detained for questioning over allegations of uranium smuggling.
Last week, state prosecutor Tshimanga Mukeba told the BBC that an "important quantity" of uranium was taken from the atomic energy centre in Kinshasa, without revealing any figures.
Mr Mushi said the release of Mr Lumu would harm the potential success of the investigation, which is continuing.
"This was a great disappointment, because we haven't yet uncovered everything there is to uncover," Mr Mushi, recently appointed as part of a new government, told Reuters news agency.
But Mr Kamanda has accused the new scientific research minister of trying to deprive DR Congo of foreign assistance in its attempt to exploit its uranium for civilian purposes.
Last August, a British newspaper, the Sunday Times, reported that uranium had been sold to Iran, a charge vigorously denied by the Congolese authorities.
Uranium is the basic raw material of both civilian and military nuclear programmes.
A mine in DR Congo's southern province of Katanga supplied the uranium that was used in the atomic bombs that were dropped by the Americans on the Japanese cities of Hiroshima and Nagasaki in 1945.
The Americans then funded the creation of DR Congo's nuclear centre in 1958.
It was established on the university campus and only for research purpose.
But in the late 1970s, a bar of uranium disappeared from the centre, raising concern about security at the site.
Moreover, the site of the centre is under risk from erosion.
People fear a landslide that could lead to a wider disaster, our reporter says.
In recent years, the International Atomic Energy Agency has visited the centre and security was believed to have improved.