South Africa's mineworkers union is urging workers to beware of what it calls "opportunists" trying to exploit recent unrest.
Strikes by miners have spread across the country since August 16, when police shot and killed 34 people during clashes at a platinum mine in Marikana township.
The National Union of Mineworkers secretary-general said anyone trying to foment trouble may be guilty of "economic sabotage," given the sector's economic importance.
Frans Baleni, who spoke to reporters in Johannesburg on Tuesday, did not refer to anyone by name.
"We want to deal with the issue of withdrawal of charges by the NPA [National Prosecution Authority] against the arrested mine workers," said Baleni. "The NUM welcomes the withdrawal of the murder charges against the 270 miners who were kept in custody over two weeks or so. We were highly perturbed by the prosecution authority, to use the common purpose laws which reminds us many of the dark days of apartheid. We believe that while the NPA has a constitutional duty to prosecute, it should do so within the law and based on concrete evidence rather than some blanket assumption."
The controversial former youth leader for the African National Congress party, Julius Malema, urged striking miners last month to make the mining industry "ungovernable." Malema was expelled from the ANC earlier this year because of previous comments that angered party leaders.
Last week, prosecutors charged 270 miners with murder in connection with last month's deaths, but dropped the charges following a public outcry.
Baleni welcomed that decision, saying the charges as initially filed were reminiscent of the "dark days of apartheid."