Lake Kivu is larger, with some two million people living on its shores and has 300 times more carbon dioxide than Lake Nyos does. However, it is thought to be less prone to such a disaster since it has a smaller concentration of CO2 in its depths.

But over the past few years it has become the place of a massive extraction of methane, which is used to generate electricity, reports New Scientist. So far, the Rwandan government has established one extraction plant on the lake and at least two more plants are in the pipeline.

If precautions are not taken and good production practices are not observed, the lake can become a giant gas bomb, warns Alfred Wüest, a bio-geochemist based at the Swiss Federal Institute of Aquatic Science and Technology. He was among a team of 15 scientists who prepared a safety report on methane production at Lake Kivu this year for Rwanda’s government.

An example of dangerous practices is pumping waste water into the lake’s shallows, where it drifts deeper due to higher density and causes mixing of water strata. With enough stirring the dissolved CO2 could start to bubble out of water and trigger a release.

However, extraction companies are inclined not to pump the waste water back where it was taken. The methane is produced by bacteria living in the depth, and extra nutrients, which the waste water draws with it, make the microbes produce more methane.

Finn Hirslund of COWI, a Danish environmental and engineering consultancy, believes that the Rwandan government puts a blind eye on the risks to secure investment. “They have failed to put in place sufficient regulations to prevent malpractice,” he says.

Rwandan officials insist that they are enforcing regulations. “All the recommendations within the report are sincerely followed,” says Eva Paul of Rwanda's Ministry of Infrastructure, but she admits that only new facilities will be obliged to follow the rules, while the government’s own plant will not be bound.