The authorities in south-west Nigeria’s Osun State have arrested 27 illegal miners, including 17 Chinese nationals and a local traditional ruler.
A government official said they would all be prosecuted and made to pay for the environmental damage they had caused.
Thousands of people work in informal mines across Nigeria which has significant mineral deposits including gold.
Correspondents say successive governments have failed to regulate the sector as they have focused on the oil industry.
Last year the authorities banned much of the gold mining activity in Zamfara State over concerns that it was linked to an escalation of violence and kidnapping in the region.
Source: bbc