1986: Hundreds gassed in Cameroon lake disaster
At least 1,200 people are feared dead in Cameroon, West Africa, after a cloud of lethal gas escaped from a volcanic lake.
The tragedy happened at Lake Nyos, about 200 miles (322 km) northwest of the capital, Yaoundé, during the night.
Most of the victims died in their sleep.
The gas killed all living things within a 15-mile (25km) radius of the lake, and the area is still highly contaminated.
It is not yet known what caused the gas to escape the lake, which lies in a volcanic crater.
Government officials say the most likely cause is a volcanic eruption in Lake Nyos which created a fissure, leaking gas into the atmosphere.
But independent scientists say this is unlikely, as the volcano is believed to be extinct.
Cameroon radio is reporting that gases are continuing to escape from the lake.
Rescue teams wearing gas masks have been rushing cylinders of oxygen to the remote area to help any who may have survived.
Hundreds of people have been arriving in the main hospital in Yaoundé for treatment.
A doctor there said they had been poisoned by a mixture of gases including hydrogen and sulphur.
He described the symptoms, including burning pains in the eyes and nose, coughing and signs of asphyxiation similar to strangulation, as like being gassed by a kitchen stove.
Eyewitnesses described how the normally clear waters of the lake turned a reddish brown, while a sudden wind arose and whipped up huge waves.
The gas is believed to have overwhelmed at least three villages.
The entire population of one of the villages is thought to have been killed.
There was a similar escape of toxic gases at a nearby lake in the same volcanic crater two years ago which killed 37 people.
The cause of that disaster, too, remains a mystery.