HSBC and other lenders have demanded China Huishan Dairy Holdings repay a combined $220 million in loans this week - a move set to make it more difficult for the firm to extricate itself from a debt mountain and find a white knight.

Billed as the nation’s largest integrated dairy firm in a high-profile $1.3 billion IPO in 2013, Huishan has since become a cautionary tale about risky financing and the complexity of resolving corporate debt problems in China.

Shares in the company, which has been heavily dependent on short-term loans, plunged 85 percent in March before being suspended.

Since then most of its directors have quit, it has missed loan payments and lost contact with a key executive in charge of its finances, and is also under investigation by Hong Kong’s securities regulator.

Huishan said late on Monday it had received letters from HSBC on a $200 million loan made by a group of banks including the UK lender in 2015, saying the loan and interest were immediately due because of “one or more events of default”.

Repayment of the $200 million loan was due within three days from Sept. 11, Huishan said in the statement to the Hong Kong stock exchange, citing a letter sent by HSBC. The demand follows a letter of warning about broken loan covenants in April.

Accrued interest added a further $6.4 million to that loan tranche. HSBC also demanded immediate repayment of a $13.7 million loan it had extended in 2014.

Hong Kong’s banking watchdog is separately questioning banks over the $200 million syndicated loan raised by Huishan from lenders including China CITIC Bank International, Hang Seng Bank (0011.HK), and HSBC, sources told Reuters in April.

Huishan said in its statement on Monday that it continued to be in talks with its major bank creditors in China about debt restructuring and that it is seeking legal advice on HSBC’s demands.

HSBC declined to comment when contacted by Reuters.

As of March this year, Huishan owed $3.9 billion to creditors including Industrial and Commercial Bank of China, Bank of China Ltd and HSBC. It has hired debt restructuring advisers and forensic accountants to investigate gaps in its financial statements.

Huishan said in July it was planning to carve up shares in the company among its creditor banks and existing shareholders as part of restructuring plans and was ultimately looking for a white knight to financially support the firm.

Huishan made headlines in 2016 when it sold and leased back part of its herd of cows, in what its executives called “innovative financing”.

But risks linked to its debt-fueled growth took center stage after a December report from U.S.-based short-seller Muddy Waters questioned its accounting and debt burden.