The World Health Organization is warning about a “high risk of biological hazard” at a Sudan laboratory of which one of the warring factions in the country has taken control.

However, officials don’t know exactly who’s behind the occupation of the National Public Health Laboratory, in the northeast African country’s capital of Khartoum, according to BBC News.

The WHO, part of the United Nations, on Tuesday told the BBC that power cuts were making it impossible to properly manage material at the lab and that lab workers can no longer access the facility.