Chinese police have arrested more than 20 people associated with “a complete Ponzi scheme” that took in more than Rmb50bn ($7.6bn) from investors, according to the official Xinhua news agency.

It is the biggest scam yet to emerge from China’s unruly and largely unregulated peer-to-peer lending sector, part of the country’s shadow banking sector. Police had to use two excavators to uncover some 1,200 account books that had been buried deep below ground, according to Xinhua.

Established in 2014, Ezubao was one of China’s highest-profile P2P lending sites, promising investors annual returns of up to 15 per cent. Ding Ning, its 34-year-old founder, allegedly ploughed new investors’ capital into its own real estate projects and also used it to pay off existing investors.