The oil company Royal Dutch Shell says engineers have capped a broken well that has been pouring out oil and gas in the Ogoni region of southern Nigeria.
Villagers complain that farm land and fish stocks have been destroyed by the spill.
The clean-up operation has not yet begun and Shell has not given details of the extent of the pollution. Oil and gas began leaking a week ago. Shell spokesman Shell believes the spill from the abandoned well was caused by sabotage. The company said pipes at the well appeared to have been sawn through, and that nuts and bolts had been removed. The BBC's Nigeria correspondent, Barnaby Phillips, says oil installations in the Niger delta are often deliberately damaged by criminal gangs hoping to receive compensation from the companies or to find employment in the subsequent clean-up.