The accident happened at around 2pm in Kampene, 180 kilometres south of town of Kindu, when "dozens of people, including children and pregnant women" were at work on the site, a civil society campaigner said.
Fourteen people were killed on Wednesday when an illegal gold mine collapsed in eastern Democratic Republic of the Congo, the government said, giving a provisional toll.
"Fourteen dead, three hospitalised with serious injuries. Search continuing," Steve Mbikayi, the minister of national solidarity and humanitarian action, said in a tweet.
The accident happened at Kampene, 180 kilometres (110 miles) south of town of Kindu.
A civil society campaigner, Justin Kyanga Asumani, also giving a preliminary toll, said "15 bodies have been recovered, including two women."
Deadly accidents are frequent in DRC's informal mining sector, especially in gold. Safety is poor and risk-taking is high.
Subsistent miners rush to an area where valuable minerals are discovered, often digging deep shafts that then collapse.
Kyanga said the accident happened at around 2pm, when "dozens of people, including children and pregnant women" were at work on the site.
In June, more than 40 illegal miners died at a copper concession in Kolwezi, southeastern DRC, that was operated by Kamoto Copper Company (KCC), a subsidiary of Swiss company Glencore.
Kyanga said the illegal mine in Kampene had been operating for around a decade, a situation that underscored "the lack of oversight and the inactivity by state bodies".