A landslide on the slopes of Indonesia's Mount Merapi volcano on Java island on Monday killed at least eight people mining sand and stones and injured eight, the country's disaster mitigation agency said. The miners had been digging out sand and stones from a steep cliff when they were engulfed, Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho said in a statement. "There could be more miners buried by the landslide, but it's unclear because the number working at the mine is also unclear," said Nugroho, noting that despite previous landslides in the area the practice had persisted. Heavy equipment had been brought in to help search for victims at the site, about 50 km (31 miles) north of the city of Yogyakarta. In many parts of Indonesia, there is little or no regulation of so-called traditional mining, resulting in poor safety standards. Nugroho said mining had persisted in the area even though landslides had occurred there before. Sitting on the so-called Pacific Ring of Fire, Indonesia has nearly 130 active volcanoes, more than any other country. The Mount Agung volcano on Bali island, east of Java, has been spewing smoke and ash intermittently for a week, disrupting flights to the tourist spot.