Livingstone set out from the mouth of the Ruvuma river, but his assistants gradually began deserting him. The Comoros Islanders had returned to Zanzibar and (falsely) informed authorities that Livingstone had died. He reached Lake Malawi on 6 August, by which time most of his supplies had been stolen, including all his medicines. Livingstone then travelled through swamps in the direction of Lake Tanganyika, with his health declining. He sent a message to Zanzibar requesting that supplies be sent to Ujiji and he then headed west, forced by ill health to travel with slave traders. He arrived at Lake Mweru on 8 November 1867 and continued on, travelling south to become the first European to see Lake Bangweulu. Upon finding the Lualaba River, Livingstone theorised that it could have been the high part of the Nile River; but realised that it in fact flowed into the River Congo at Upper Congo Lake.