The state-run mine collapsed Saturday afternoon in the province of Samangan, trapping about 60 people, the Wall Street Journal reported.
Rescue efforts were ending Sunday afternoon, local time, said Mohammad Rafi Sediqi, a spokesman for Afghanistan's Ministry of Mines and Petroleum.
Investigators were looking into whether local Taliban militants, who were reported as being in the area at the time of the collapse, played a role in the incident, Sediqi said.
"It's not clear at this time," Sediqi said. "We are working on it."
Afghan President Hamid Karzai issued a statement expressing condolences to the families of the victims.