Two people were found guilty on Thursday of masterminding Singapore’s “most serious case” of market manipulation, wiping S$8.0 billion (US$5.8 billion) in a penny-stocks scam nearly a decade ago.

Malaysian John Soh Chee Wen and Singaporean Quah Su-Ling were convicted of using over 180 trading accounts to inflate the share prices of three companies.

Prosecutors called it the “most serious case” of stock market manipulation in the city-state’s history and detailed how the accused planned a “complex and elaborate fraud” to manipulate the share prices of Blumont Group, Asiasons Capital and LionGold Corp.

Soh and Quah used the shares as collateral, convincing several banks – including Goldman Sachs – to extend more than S$170 million ($123 million) in credit to finance their scheme.

They then used this cash to create demand for penny stocks, reportedly managing to push up some prices by around 800 percent in 2013.

But on October 4, prices crashed, wiping an estimated S$8.0 billion from the Singapore Exchange.

Singapore authorities say the incident dented investor confidence and directly affected trading.

High Court Judge Hoo Sheau Peng convicted Soh of 180 out of 188 charges and Quah of 169 of 177 charges.

The judge said he was “satisfied beyond reasonable doubt that there existed a conspiracy between the two accused persons to manipulate the market” .

Both will be sentenced at a later date. They face multiple years in prison and hefty fines, the police and the central bank said in a joint statement.

Soh has been under remand since the duo was first charged in 2016, while Quah is out on bail.