The men are believed to have drowned after water from a burst dam flooded the shafts and underground tunnels they were working in.
Police said rescue teams were trying to pump out the water and search for bodies and any survivors.
According to reports, illegal miners in Battlefields, 175 km west of Harare, had entered shafts on land owned by RioZim and another firm in search of gold.
It added that the two mines, called Silver Moon Mine and Cricket Mine, are run by registered companies.
US military says it turned away blockade runner trying to reach Iranian port
The US military has announced that it fired a missile into the engine room of a vessel trying to get through the US blockade of Iran on Friday.
WHO chief urges safe burials in visit to heart of Ebola outbreak
The World Health Organisation (WHO) chief has travelled on Saturday to the Congolese province hardest hit by an Ebola outbreak, urging residents to seek treatment and practice safe burials as officials scramble to contain the fatal disease.
Rescuers pull four from flooded cave in Laos
Rescuers pulled four people from a flooded cave in Laos on Saturday, Thai volunteers said, hours after another man was brought out late on Friday.
Brazil investigates suspected Ebola case in Sao Paulo
Health authorities in Brazil's Sao Paulo state are investigating a suspected case of Ebola reported on Saturday in the state capital, officials said.
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