By Devon Maylie

JOHANNESBURG--Police are investigating the deaths of two mine workers outside a mine run by Forbes Coal on Wednesday, after security guards dispersed a crowd of protesters.

Workers at Forbes Coal & Manhattan Coal Corp.'s (FMC.T) Magdalena and Aviemore mine in Kwa-Zulu Natal, South Africa, had gone on strike earlier this month to demand higher wages. On Wednesday, police said a group of 100 workers gathered outside the mine and were dispersed by security guards.

"It is alleged that some of the workers attempted to break into an armory on the mine and they were dispersed by mine security. It is further alleged that the security officers chased some of the workers into an informal settlement near the mine and shots were fired, injuring two men," said police spokesman Jay Naicker.

Colonel Naicker said both men were taken to the hospital but later died from their injuries and that police are now are investigating two counts of murder. Police have seized firearms from all the security guards that were on duty as part of an effort to find the shooters.

Forbes Coal Chief Executive Stephan Theron said in a statement that it closed the mines and that it's "committed to the process of responsible discussions."

The deaths come weeks after police fired live ammunition into a crowd of protesting miners outside platinum producer Lonmin Plc's (LMI.LN) Marikana mine, killing 34 people in some of the worst post-apartheid violence to hit South Africa. In all, 46 people died during the Lonmin strike.

Since the August shooting at Lonmin, violent strikes spread across the mining industry, shutting some of the country's biggest platinum, gold and iron ore mines. Most of the strikes have been resolved through wage increases, but the strike continues at the world's largest platinum producer, Anglo American Platinum (AMS.JO).

On Tuesday, workers at Anglo Platinum's Rustenburg mines clashed with police, who fired rubber bullets and tear gas on a group of about 1,000 protesters. The company said 12,000 miners it had dismissed earlier in the month and all others on strike had until Tuesday morning to return or lose their job for good. The company hasn't commented since Tuesday.

The strikes are not only threatening to cause more violent uprisings outside mines, but they're threatening the country's economy and could increase unemployment.

Lonmin this week issued a notice to unions that it will begin a consultation process that could lead to job losses starting in January, primarily at management levels.

And on Wednesday, government data showed that South Africa's trade deficit widened unexpectedly to 13.8 billion rand ($1.6 billion) in September, a grim confirmation of the toll that labor turmoil is taking on the continent's largest economy.

The trade balance added ZAR1.6 billion to a deficit of ZAR12.2 billion in August, according to data from the South African Revenue Service. Exports fell 7.7% on the month in September, the data showed, thanks largely to declines in the mining industry.

The sector, responsible for more than half of South Africa's exports, already led the country's finance minister last week to lower South Africa's growth outlook again to 2.5% this year, down from his previous forecast for 2.7% growth in 2013.

--Patrick McGroarty contributed to this report

-Write to Devon Maylie at devon.maylie@dowjones.com