The troubles facing Singaporean oil trading firm Hin Leong deepened as the city-state’s police have started investigating the company.

The probe, which the Singapore Police Force confirmed by email, is the latest twist in the downfall of the company, which owes $3.85 billion to more than 20 banks and revealed in court filings that it hid about $800 million in losses. Hin Leong didn’t immediately respond to emails and a phone call seeking comment Tuesday morning in Singapore.

The implosion of Hin Leong Trading (Pte) Ltd., one of the biggest and most secretive players in the world of physical oil trading, is among the most spectacular impacts wrought by this year’s collapse in oil prices, which squeezed the firm’s revenues and triggered banks to call in debts