Twenty-four West African migrants were rescued and dozens more feared dead after traffickers deserted them in Niger's northern desert without food or water, a senior local official said.
The migrants rescued on Sunday were part of a group of "70 people who had left in three vehicles from Agadez for Libya," Fatoumi Boudou, the prefect of the northern region of Bilma.
Agadez is a remote town in Niger on the edge of the Sahara that has become the smuggling capital of Africa.
The traffickers "abandoned them in the middle of the desert without food or water," he said, adding that those rescued had spoken of several dead bodies without specifying a number.
But the Agadez-based Air Info website, citing a security source, said scores of bodies had been buried on Sunday by troops and locals.
A local radio station had said 52 dead bodies had been discovered by authorities on Sunday.
The 750-kilometre (465-mile) trip from Agadez to the Libyan border takes between two and three days with only very short petrol and toilet stops on the way.
Boudou said searches across a 65-kilometre radius had yielded one dead body "with the identity card of a Nigerian student."
In early June, at least 44 Libya-bound migrants, including women and babies, died of thirst in the Sahara desert after their vehicle broke down in scorching conditions.
In May 2015, the government in Niamey adopted a law banning the illegal trafficking of migrants with those found guilty facing a prison sentence of between one and 30 years, and fines of up to 30 million CFA francs (45,000 euros/$51,000).
Libya has long struggled to control its southern borders with Sudan, Chad and Niger, even before the 2011 uprising that toppled dictator Moamer Kadhafi.
In the chaos that followed, traffickers stepped up their business, with tens of thousands of people each year making the perilous crossing to Italy just some 300 kilometres away.
Germany and Italy last month called for an EU mission to be installed on the border between Libya and Niger to reduce the migrant flow.