KINSHASA (AFP) - A plane carrying 15 UN and private aid workers and two crew slammed into a mountain in eastern Democratic Republic of Congo and the plane's operator said Tuesday there were no survivors. There were at least three foreign workers - including a Canadian and an Indian - on the small jet chartered by the Air Serv company which said it crashed in the Kahuzi mountains about 15km northwest of the city of Bukavu. The US-based airline which specialises in operations for humanitarian groups said in a statement that a helicopter had flown over the wreckage and there were "no known survivors". It said the "last known radio contact was made 10 minutes inbound to Bukavu in heavy rain" late Monday. Air Serv and the UN said there were 15 passengers and two crew. Helicopters from the UN mission in DR Congo (MONUSC) had spotted the debris, said a Kinshasa spokesman for the UN Office for the Coordination of Humanitarian Affairs (OCHA). "It is not yet known if there are survivors," said the spokesman, Christophe Illemassene. The company said the plane was on a flight from Kinshasa to Mbandaka, Kisangani and Bukavu when it crashed into a steep ridge.  It was reported missing late Monday when it failed to land on schedule in the South Kivu provincial capital. UN sources in Kinshasa said there were at least three foreigners - including a Canadian and an Indian - on board and the rest of the passengers were Congolese. Many were employed by the UN Development Programme (UNDP) and the NGO Handicap International, a senior official at Bukavu airport told AFP. The aircraft broke into several pieces when it hit the ground, the official, Jean-Marie Vianney Bikoro, said. The weather was reported to have been particularly bad in the South Kivu region on Monday, UN sources said. Financed by international donors, Air Serv carries humanitarian aid workers throughout DR Congo. It also operates in Chad, Uganda, Mozambique, Iraq and Afghanistan.