(Bloomberg) –NMC Health Plc shares plunged after two major investors sold $493 million worth of shares well below the market price to reduce their holdings in the troubled health-care group.

The stock fell as much as 19% to 1,206 pence in early London trading. Investors Saeed Mohamed Butti Mohamed Khalfan Al Qebaisi and Khaleefa Butti Omair Yousif Ahmed Al Muhairi both sold about 15% of NMC for about 1,200 pence a share.

The company had a rocky end to 2019 as shares slumped following allegations by Carson Block’s Muddy Waters Capital LLC. The short-selling firm said the company’s financial statements hint at potential overpayment for assets, inflated cash balances and understated debt.

NMC, which is based in the United Arab Emirates, has said that those claims are unfounded and that it would conduct an independent review.

The two investors will retain a combined stake of about 17% in the company and agreed to place their remaining shares in a temporary lock-up. Proceeds from the sale will be used to pay down debt.