NIAMEY, Nov 8 (Reuters) - At least 18 people were killed on Sunday in an artisanal gold mine collapse in southern Niger, the local mayor said on Monday. The disaster took place in the southern Maradi region, near the border with Nigeria. The death toll is likely to rise, said Adamou Guero, mayor of the commune of Dan Issa. "When we arrived at the site yesterday, people were still searching for bodies," he said. "It"s something which is common in gold mines. It"s very difficult to control," Guero added. Artisanal miners often use old-fashioned and unregulated methods of digging, leading to frequent deadly accidents. Increasing demand for metals and rising prices have triggered a boom in small-scale mining in poor countries around the world in recent years. The activity is common across much of West Africa.