South Africa's police ministry says more than 30 people were killed when its officers opened fire on striking workers at a Lonmin PLC mine.

Police ministry spokesman Zweli Mnisi gave the figure Friday after Thursday's shooting in Marikana, just northwest of Johannesburg.

Mnisi said the country's police minister planned to address journalists later Friday. He said an investigation into the shooting has begun.

The protest and ensuing violence at the platinum mine, which began a week ago, has killed at least 10 people there, including two police officers. It's also drastically affected production at the mine.