Eleven people were admitted to hospital in South Africa on Friday after they came into contact with an envelope suspected to contain anthrax powder, police said.
Inspector Juanita Kilian said police had received a complaint from the post office in the district of Alberton, south of Johannesburg, about a "suspicious" envelope, she told public radio.
"The envelope was filled with powder ... At this stage we cannot confirm that the contents were anthrax," said Kilian.
The scene had been decontaminated and those affected have been taken to hospital for medical treatment, she said.
The envelope was taken to a police laboratory in the capital Pretoria for forensic testing.