Forty-nine people died of thirst in an isolated Sahara desert district in Niger after the truck transporting them broke down, authorities said Thursday.

The dead were among a group returning from Mali for a Muslim festival when they ran short of water, the Agadez governorate said in a post on Facebook.

The 49 people “died of thirst in a remote area more than 80 kilometres (50 miles) west of Assamaka”, added the statement. Assamaka is a main crossing point between Niger and Algeria but also close to the Mali frontier.

“Deprived of water and unable to repair the vehicle despite the efforts of the driver, his assistants and the passengers, the travellers found themselves trapped in the heart of a hostile environment where extreme temperatures and the absence of supply points make survival extremely difficult,” the governorate detailed, adding that the victims were buried in mass graves.

Two people however managed to survive after walking more than 50 kilometres on foot to a nearby water source and then onwards to Assamaka, where the pair were able to alert the authorities, the governorate said.

The desert zone is a known transit point for migrants seeking to get from African nations to Europe and many have died from thirst or starvation in the scorching sands.