As in Angola, during the 18th century Afro-Portuguese traders employed by the Mozambican prazo owners penetrated inland from the Zambezi valley as far as Kazembe in search of ivory and copper. In 1798 Francisco de Lacerda, a Portuguese officer based in Mozambique, organised an expedition from Tete to the interior hoping to reach Kazembe, but he died en route in what is now Zambia. Apart from Lacerda's expedition, none of the trading ventures into the interior from Angola or Mozambique had official status and were not attempts to bring the area between Angola and Mozambique under Portuguese control. Even Lacerda's expedition was largely commercial in purpose, although it was later claimed by the Lisbon Geographical Society to have established claim to the area Lacerda covered. In 1831 Antonio Gamitto tried without success to establish commercial relations with Kazembe peoples in the upper Zambezi valley.