The miners were killed in an explosion in the mine, which occurred in the early hours of Wednesday.
According to local media reports, the miners were said to have inhaled poisonous gases from the explosion.
The report by Ghanaian Times on Thursday said that a source at the Bolgatanga Teaching Hospital confirmed that they died from poisonous gases.
It added that 13 bodies were retrieved from the pit initially, but the death toll has risen to 15.
The government had earlier placed a ban on the activities of illegal mining in the country, but lifted the ban recently after streamlining their activities.