A large crowd has gathered near the site of a South African mine where 34 people were killed Thursday after police opened fire on striking miners.

Some of those who gathered Saturday near the Lonmin PLC platinum mine, northwest of Johannesburg, sat and wrapped themselves in blankets to protect themselves against the chilly weather.

Authorities continue to investigate the incident, South Africa's deadliest security operation since the end of apartheid.

South Africa's national police chief, Riah Phiyega, says her forces opened fire in self-defense against striking mine workers. In addition to the 34 deaths, 78 people were injured.

Phiyega said police used force to protect themselves after coming under attack by strikers armed with “dangerous weapons.”

On Friday, South African President Jacob Zuma ordered an official inquiry into the incident. He said he was “shocked and dismayed” at what he called “senseless violence.”

About 3,000 people have walked off the job at the mine in the past week due to a pay dispute. Lonmin is the world's third-largest platinum producer.

Before Thursday's confrontation, mine managers had warned workers they would be dismissed if they did not return to work by Friday.