A number of blasts were blamed on right-wingers
Police have conducted raids on homes in six of South Africa's nine provinces in a hunt for white right-wing militants.
One person was arrested for illegal possession of explosives, with police saying they expect more arrests to follow.
There have been several similar raids over the past few months, following a series of bomb attacks, which killed one person in Soweto.
Twenty-three right-wingers are due to face trial in Pretoria in May for trying to overthrow the government through violence.
Another 24 people have been arrested for contravening firearms legislation.
Police spokeswoman Sally de Beer said the swoop was fourth such operation, code-named Hopper, since November last year.
"The focus of Hopper IV is on people about whom the police have received information during the course of our investigation into a plan to overthrow the government," she told AFP news agency.
Since the end of apartheid, a small group of conservative whites has remained opposed to democratic rule.
Police have linked a group called the Boeremag, or Boer Force, to the blasts.
President Thabo Mbeki says government information has indicated "that the right wing have the intention to conduct a campaign" to destabilise South Africa.
But analysts like Martin Schonteich, of the South African Institute for Security Studies, says the far right has neither the capacity nor the allies to pose a real threat to the government.