The aircraft was contracted by Air Serv International.
United Nations helicopters have been circling the wreckage, but so far there are no signs of life, UN rescue teams said.
The plane had been on its way to Bukavu from the city of Kisangani on Monday when it lost contact with ground control as it made its landing approach in bad weather at around 1200 GMT.
The difficult mountainous terrain and bad weather meant rescue teams could not reach the wrecked plane on Tuesday.
Amy Cathey, Air Serv regional manager, said UN rescue teams were “securing the site and searching for and recovering victims’ bodies”.
The passenger manifest said the flight was carrying aid workers from the Dutch branch of medical charity Medecins Sans Frontieres, Handicap International, the UN humanitarian agency Office for the Co-ordination of Humanitarian Affairs (OCHA) and and the UN Development Programme (UNDP).
The manifest also showed that six foreigners were from France, India, Canada, Congo-Brazaville [DRC’s neighbour], South Africa and Britain.
The remaining 11 passengers were listed in the manifest as citizens of the Democratic Republic of Congo.
Many agencies arrange their own air travel for staff in DR Congo because of the country’s poor air safety record.