Thirteen scrap-metal collectors in northeast Nigeria's Borno state were killed when a bomb they excavated blew up, security sources said on Tuesday.
Sixteen metal scavengers from a displaced persons' camp in Bama found the bomb while digging for scrap on Monday in the bush on the outskirts of town.
Bama is located in a region that has seen prolonged conflict between the Nigerian government and jihadist insurgents.
"The bomb exploded as they were pushing it in a cart toward the town, killing 13 and seriously injuring three.
Nigeria's military is battling to end a 13-year jihadist insurgency in the country's northeast that has killed more than 40,000 people and displaced 2.2 million more.
Boko Haram seized Bama in 2014 when they took over of territory in northern Borno and declared a Caliphate.
In March 2015 Nigerian troops aided by Chadian soldiers clawed back most of the territory after months-long intensive ground and aerial operations.
Residents who had fled the town returned three years later, with many of them living in displaced camps as the town was substantially destroyed during the fighting to retake it.
Most of the displaced who live in camps rely on food handouts from aid agencies, forcing many to turn to felling trees in the arid region for firewood and scavenging for metal scraps which they sell to buy food.
Jihadists have been targeting scrap collectors, accusing them of spying for troops and the militia fighting them.