A South African businessman has been charged with violating laws against the proliferation of weapons of mass destruction.
Mr Meyer is to remain in custody until next week
Johan Meyer, 53, who owns an engineering plant south of Johannesburg, denies the charges.
"He was arrested on charges that he was building a nuclear weapon," said his lawyer, Heinrich Badenhorst.
The charges follow a lengthy police investigation, which involved the UN nuclear watchdog, the IAEA.
They also follow the arrest last year of a South African man in the US, who was charged with smuggling devices used to detonate nuclear weapons to Pakistan.
The authorities say they have seized items from Mr Meyer, but are releasing few details.
According to the official charge sheet, he was accused of offences between 2000 and 2001 relating to the import and export of regulated goods "which could contribute to the design, development, manufacture and deployment" of weapons of mass destruction.
He was also accused of "unlawfully and wilfully possessing... nuclear-related equipment and material" from 2002 to 2004.
He will stay in custody until his bail hearing, set for next Wednesday, 8 September.
If found guilty, he could serve a lengthy jail sentence.
The old apartheid regime in South Africa had a nuclear weapons programme.
But this was closed down by the white government before it relinquished power in 1994.