DAKAR, Senegal (AP) — The International Organization for Migration says 51 migrants are presumed dead in the Sahara Desert in Niger after smugglers abandoned them during their journey north to Libya.

The group said Tuesday that some 24 migrants from Gambia, Nigeria, Senegal and Ivory Coast alerted authorities days ago that they had been stranded. The organization said the survivors were taken to Seguedine, where one died. They will be transferred to the Dirkou center Tuesday.

The survivors said they were in a group of 75 taking three different cars. The organization said authorities are searching for the 51 bodies after sand storms.

IOM says it has saved more than 600 migrants since April 2016 in Niger, which is a major route for West African migrants making their way toward Europe.