A South African man accused of threatening to unleash biological weapons on Britain and the United States unless he was paid millions of dollars was arrested Saturday, police said. Authorities said they had not found evidence he was capable of carrying out the threats.

In a statement, South African police said a six-month terror investigation by South African, British and U.S. officials culminated with the arrest of the suspect in northwestern South Africa. Police spokeswoman Sally de Beer said the businessman would not be named until he appears in court Monday in Johannesburg.

"This biological agent, if deployed, would have caused the destruction of property and resulted in major economic loss," the police statement said. "This was therefore regarded as a very serious threat."

De Beer said the threats were made repeatedly in letters and e-mails. Police were searching the man's home and other sites, de Beer said Saturday.

The suspect threatened to carry out the threats unless he was given $4 million.

U.S. Embassy spokeswoman Elizabeth Trudeau said she could not discuss the specifics of the investigation.

"However we can confirm that this was an ongoing and close collaboration with the South African Police Service, Scotland Yard and American law enforcement based at the U.S. Embassy," she said.

Scotland Yard confirmed that its counterterrorism officers had provided support to the investigation but declined further comment.