At least 49 people died of thirst after a truck broke down and they were stranded for days in the Sahara Desert in northern Niger, authorities said.

The victims, all Nigeriens, were returning home from a religious festival in Mali when the truck stopped running more than 80 kilometers (49 miles) west of Assamaka, near the borders with Mali and Algeria, Niger’s Agadez region governorate said in an online post late Thursday.

Two men survived after trekking more than 50 kilometers (31 miles) to a water source and then continuing to Assamaka, where they alerted authorities, the governorate said.

A delegation sent to the scene by the Agadez Region Governor Gen. Ibra Boulama Issa learned the truck had traveled for several days from the Malian town of Talhandek about 300 kilometers (187 miles) from the Nigerien border.

It was not immediately clear what led to the breakdown or how long the passengers waited.

“On the spot, the findings were particularly disturbing. Dozens of lifeless bodies were found under the immobile truck and in its surroundings,” the Agadez governorate said.

Photos published by the governorate showed bodies in the desert with pieces of clothing and other belongings scattered around.

“Deprived of water and unable to repair the vehicle despite the efforts of the driver, his apprentice and passengers, travelers found themselves trapped in the heart of a hostile environment where extreme temperatures and lack of supply points make survival extremely difficult,” the governorate said.

The 49 victims were buried in mass graves at the scene in what officials called a “particularly delicate and emotionally exhausting task” for the survivors.