Protesters gather at the Lonmin platinum mine in Marikana, South Africa on August 17, 2012 where the day before 34 people were killed when police opened fire on striking mineworkers. 
Striking South African miners armed with homemade spears and pangas chant slogans near the Marikana platinum mine on August 16, 2012. Rising tensions at the mine exploded into grisly violence after police opened fire on striking miners. 
Striking workers are monitered by police during a sit-in on a hill as they demad a wage increase. 
A police vehicle takes position as miners sit on the hill. 
Armed workers chant slogans outside the mine. 
Workers sit together on strike. 
A policeman fires at the participants of the protest. 
Policemen fire at the striking miners. 
A policeman gestures in front of some of the miners after they were shot. 34 workers were killed in the violence. 
Policemen keep watch over striking miners after they were shot. 
A policeman gestures in front of some of the dead miners. 
- The striking miners join 28,000 others who walked off the job at another mine
- Violence at Lonmin's Marikana platinum mine left 44 people dead last month
- The company set a Monday deadline for returning to work
Johannesburg (CNN) -- Operators of a South African gold mine negotiated with about 15,000 striking workers Monday after they walked off the job the night before, a company official said.
"At this stage, the reason for the strike remains unclear, but we hope to gain clarity as soon as possible," said a statement from Peter Turner, a Gold Field executive vice president. "The situation in the mine has been calm and peaceful since the start of the strike, and we appeal to all stakeholders to continue to act with restraint and to engage in good faith.
"It is important that we restore normality in a peaceful manner and as soon as possible," he said.
Management called the strike at the KDC Gold Mine on the West Rand "Unlawful and unprotected."
Striking miners want wages doubled 
Life of a miner in South Africa 
Miners celebrate release from jail The striking miners could not immediately be reached for comment.
The KDC workers join about 28,000 other miners who are already on strike at the Lonmin PLC platinum mine in Marikana, about two hours northwest of Johannesburg.
August 16 clashes at the Lonmin mine left 34 people dead and 78 wounded, sparking national outrage.
Management at Lonmin set a Monday deadline for strikers to return to work, but workers did not appear to heed the call, as several thousand were marching outside the facility.
The violence in August erupted after negotiations between striking workers and Lonmin broke down and police decided to fence in the machete-armed miners with barbed wire, police said. Thousands of mineworkers had been striking for days for higher wages.
Lonmin has so far missed out on around $75 million in lost production, and the workers haven't been paid for a month.
The company said last week that a "peace accord" had been signed, but key unions had not agreed to the deal.
Late last month, a regional prosecutor charged 270 of the platinum miners with the murder of their colleagues, who are believed to have been shot by police.
However, a national prosecutor has said that authorities would dismiss the provisional charges and release the miners, pending further investigation.
South Africa drops murder charges against miners
Last week, 47 of the miners appeared in court and were ordered released.
Lawyers for the miners had called the decision to charge them with murder "bizarre in the extreme." The country's justice minister called the charges shocking and confusing.
Clashes also erupted last week between protesters and security officers outside Gold One's Modder East gold mine in Springs, about 24 miles (39 kilometers) east of Johannesburg, police said. The violence occurred after former employees staged a protest outside the mine's gates, Johannesburg police Capt. Pinky Tsinyane said.
The protesters had been fired for participating in an earlier illegal strike, the company said.
CNN's Aja Harris contributed to this report.
