The Somali region of eastern Ethiopia has been affected by a mystery illness. Over the past few years, hundreds have died.

The deadly sickness is striking mainly nomadic communities who roam the Ogaden Basin, where companies, some of them foreign-owned, have been prospecting for oil and gas.

A regional official said more than 2,000 people had died from the mystery illness. An unknown number of others have become very sick.

Juweria Ali, a human rights researcher who has spent months investigating the issue, says the symptoms are horrific and include nosebleeds, eyes turning green or yellow, really high fever, fainting and ultimately death.

Ms Ali says the illness could be related to the activities of those hoping to exploit what are believed to be vast reserves of oil and gas - although scientific studies would be needed to prove this.

"Locals describe seeing white powder spilled in their neighbourhoods by companies operating. When it rains, these toxins then flow into the river, which people drink - so it's a vicious cycle," she said.

Companies operating in the area have declined to comment on the chemical spillages.

So have the Ethiopian authorities, despite increasing demands from the affected communities that they take some kind of action:

"Government officials in Addis Ababa have completely denied the existence of any health or environmental issues. In fact one official denied that anyone even lives around the area, which is of course contrary to what we know," said Ms Ali.

Prime minister Abiy Ahmed has said oil and gas are an essential part of Ethiopia's future, and will generate much needed jobs.

But previous attempts to exploit the Ogaden Basin's precious resources have run into trouble - Emperor Haile Selassie was forced by mass demonstrations to abandon a project.

Rebels have also been active in the area. In 2007 they stormed a Chinese-run oilfield, killing 74 people. It is possible this mystery illness could further delay efforts to exploit these valuable resources.