Lava from a volcano in a sparsely populated area of the Democratic Republic of Congo is threatening rare chimpanzees, wildlife officials say. Mount Nyamulagira, 25km (16 miles) from the eastern city of Goma, erupted at dawn on Saturday, sending lava into the surrounding Virunga National Park. About 40 endangered chimpanzees and other animals live in the area. But the country's famous critically endangered mountain gorillas are said to be safe as they live further east. Emmanuel de Merode, Virunga's director, said that park staff were working with the civilian and military authorities to assess the risk and take appropriate action. Rangers were deployed to the area to monitor the flow of lava and were due to report back hourly, he added. A government official, Feller Lutahichirwa, said observers were monitoring the situation with help from UN helicopters, the Associated Press reports. ,b>'Mountain on fire' While few people live in the area immediately affected, officials said their primary concern was to protect human settlements. Innocent Mburanumwe, warden for Virunga's southern sector, said that lava was flowing towards an area to the south of the volcano, where "many people" live. "I was woken at 0345 [0145 GMT] by a loud bang, which I first thought was the sound of war," he added. "I thought there was fighting again near our park station," he said, referring to the conflicts which have wracked eastern DR Congo. "Then I saw the mountain was on fire with sparks flying." Mount Nyamulagira (also spelled Nyamuragira), which stands at 3,058m (10,033ft), is one of the most active volcanoes in Africa, according to officials in Virunga. It has registered more than 35 eruptions since 1882, with the most recent before this weekend being in 2006. Virunga, a Unesco World Heritage Site since 1979, is home to 200 of the world's 720 remaining mountain gorillas but they live on the flanks of the Mikeno volcano further east from Nyamulagira. Previous eruptions of the volcano have threatened the city of Goma, which has a population of at least 200,000 as well as tens of thousands of refugees. Source: BBC