Abu Dhabi Commercial Bank initiated criminal legal proceedings with the attorney general in Abu Dhabi against a number of individuals in relation to NMC Health group.
“This action is consistent with the bank’s objective to protect its interests," the lender said in a statement on Wednesday.
"ADCB continues to work closely with other creditors and the joint administrators to ensure continuity of NMC Health’s operations and rapid recovery of the business."
The bank, which is the embattled hospital operator's biggest sole creditor, did not specify who it had initiated criminal proceedings against.
A UK court placed NMC Health into administration on the application of ADCB last week.
The bank has an exposure of $981 million (Dh3.6 billion) to NMC. Overall, UAE banks have a combined exposure of at least Dh8bn to the healthcare firm. NMC also owes money to Oman-based banks and financial institutions.
The latest development comes as Alvarez & Marsal, the joint administrators of the embattled firm, appointed a new set of board members "to ensure more robust standards of governance" at the company.
The four new non-executive directors – Eli Chahin, Christopher Hall, Myles Halley and Philip Gore-Randall – have broad international restructuring experience, according to a company statement earlier this week.
Following the appointment of administrators, the previous board members "ceased to have decision-making powers" and have been removed from the board, it added.
NMC Health's lenders are also forming a coordinating committee, with a steering group acting as the primary contact between the company and its debtors. ADCB will chair the co-ordinating committee while the steering group will consist of other significant creditors, including Abu Dhabi Islamic Bank, Dubai Islamic Bank, Barclays and Standard Chartered.
Over 80 major local, regional and international financial institutions extended credit to NMC, which was founded by BR Shetty in Abu Dhabi in 1975, and now employs more than 2,000 doctors and about 20,000 other staff.
It operates 2,200 hospital beds as well as clinics and pharmacies in 19 countries.
The company has made a series of damaging disclosures in the past few months after a report by activist investor Muddy Waters in December alleged it inflated cash balances, overpaid for assets and understated its debt.
Last month, NMC revealed its debt stood at $6.6bn, substantially higher than the $2.1bn declared in its last filed accounts. A review committee also discovered evidence of “suspected fraudulent behaviour”.
In February, the UK’s Financial Conduct Authority launched an investigation into NMC's activities after the company's shares were suspended from trading on the London Stock Exchange.
NMC Health appointed Ithmar Capital’s managing partner, Faisal Belhoul, as executive chairman on March 26 after the Dubai-based private equity firm took a 9 per cent stake in the healthcare company.
The company dismissed its former chief executive, Prasanth Mangath, in February.