JOHANNESBURG — Prosecutors provisionally dropped murder charges against the 270 jailed miners who had been accused under an obscure legal doctrine of killing 34 of their own colleagues when the police opened fire on them while engaged in a wildcat strike.

The police fired live ammunition into a crowd of about 3,000 platinum miners armed with clubs and machetes while trying to disperse the illegal strike on Aug. 16. When the firing stopped, 34 miners were dead and South Africa was outraged by the bloodiest confrontation between the police and civilians since the end of apartheid. The police have claimed they acted in self-defense.

The outrage grew when prosecutors announced last week that under a legal doctrine known as “common purpose,” the miners would be charged with murdering their colleagues. Under the doctrine, which was frequently used in the waning days of apartheid to charge members of protesting crowds with serious crimes committed by a few individuals, people in a mob can be charged as accomplices.

In a hastily arranged news conference Sunday, officials from the National Prosecuting Authority said that they would await the outcome of further investigations into the shootings, but they did not rule out bringing murder charges again.