The Zambian government has dropped charges against two Chinese managers accused of attempted murder after firing on miners during a pay dispute.
Xiao Li Shan and Wu Jiu Hua said the workers' behaviour, at the Collum coal mine in October, had been threatening. The shooting left at least 11 injured.
China has invested more than $400m (£250m) in the copper-rich country.
But companies have faced regular opposition from workers and union leaders over abuses and low wages.
Mr Xiao and Mr Wu had opened fire indiscriminately on their employees at the mine in Sinazongwe to break up a protest, according to police.
Following the decision to drop the charges, their defence lawyer, George Chisanga, said Zambian law meant the state did not have to give an explanation and the pair could still be called back to court by the director of public prosecutions.
Reuben Lifuka, the president of anti-corruption group Transparency International Zambia, warned the move could damage confidence in Zambia's judicial system.
"The trauma and injustice that the mine workers suffered is public knowledge and the government itself has on several occasion reprimanded the managers of coal mine on the poor working conditions," he said.