LONDON/HONG KONG (BLOOMBERG) - Bank of America has told investment bankers to stop working on transactions with HNA Group for now amid growing concerns about the acquisitive Chinese conglomerate's debt levels and ownership structure, according to people familiar with the matter.

The US investment bank joins other Wall Street firms, including Citigroup and Morgan Stanley, that are largely steering clear of advising and financing the group on deals because they are unable to get internal approvals from "know your customer" committees, the people said, asking not to be identified because the information is private.

Bank of America had advised HNA on several attempted overseas acquisitions in the past few years, people said. The decision has affected deals the firm was working on for HNA, including the planned Singapore IPO of HNA Commercial Reit, two of the people said. The Reit was expected to raise some S$700 million.

Banks regularly reassess their comfort with potential clients, and their stance towards HNA could change, they said.

HNA has not done significant fee-paying business with Bank of America in recent months, one person with knowledge of the company said.

Senior officials at Bank of America's Merrill Lynch unit communicated internally last month that bankers should not currently pitch for new acquisitions and fund-raisings, the people said. Scrutiny of Chinese companies came into focus this week after people familiar with the matter said that China plans to cut off some funding for billionaire Wang Jianlin's Dalian Wanda Group, concluding the conglomerate breached restrictions for overseas investments.

An internal memo at Bank of America on holding off on deals with HNA for now went to fewer than five bankers who would be in a position to solicit business from the Chinese company, another person familiar with the matter said. The New York Times reported earlier that Bank of America had said in an internal e-mail that it had decided to remove itself from transactions with HNA.

Citigroup's and Morgan Stanley's internal committees have also struggled to get sufficient clarity on the source of funds and ownership structures at HNA, leading those banks to avoid deals for some time, the people said. Still, some firms that shy away from the parent company are willing to do business with HNA units. Morgan Stanley was one of the banks that committed to a total US$8.5 billion (S$11.63 billion) in financing for Avolon, a business owned by one of HNA's listed arms, in its purchase of CIT Group Inc.'s airline leasing business last year.

A representative for HNA could not immediately comment. Representatives for Bank of America, Citigroup and Morgan Stanley declined to comment.

Support from Western banks has helped fuel a debt-backed buying spree by HNA, as it expanded from its home base on China's sunny Hainan island to add logistics, hotel and financial assets around the globe, including a US$6.5 billion deal to buy a stake in Hilton Worldwide Holdings announced last year. Chinese regulators have begun assessing local banks' loan exposure to HNA and are examining examples of acquisitions gone awry, people with knowledge of the matter have said.

Still, banks including JPMorgan Chase & Co and UBS Group have financed and advised on large HNA deals this year, notably the Hilton stake and the firm's acquisition of a 10 per cent stake in German lender Deutsche Bank AG.

Even UBS, which has historically helped HNA on multiple transactions, has started monitoring the conglomerate's debt levels more closely, separate people said. The Swiss bank is increasingly concerned that the Chinese company would struggle in the short term to complete large acquisitions, according to one of the people. UBS continues to do business with HNA, though its internal risk and compliance teams have begun asking more questions about dealings with the Chinese firm, another person said.

UBS advised HNA on its US$1.5 billion acquisition of Gategroup Holding, which completed this year. The Swiss lender has been one of the most active bankers for HNA, advising the firm on almost US$15 billion of aviation-related acquisitions since 2015, according to data compiled by Bloomberg. It also provided collar financing to help the conglomerate increase its stake in Deutsche Bank, people familiar with the matter said in May.

A spokesman for UBS declined to comment.

The pushback comes as HNA has been working to raise its profile in the West, hosting the French Open tennis tournament this year, a first for the firm. Executives including chairman Li Xianhua and chief executive officer Adam Tan kicked off with a gala celebration in Le Petit Palais in Paris that included politicians, bankers and celebrity chef Joel Robuchon.

HNA has recently told bankers it plans to slow the pace of its overseas dealmaking, according to one of the people with knowledge of the matter. The move comes as acquisitive Chinese companies are under increasing scrutiny at home. The China Banking Regulatory Commission asked some banks to provide information on overseas loans made to Dalian Wanda, Anbang Insurance Group, HNA, Fosun International and the Chinese owner of Italian soccer team AC Milan, people familiar with the matter said in June.

China is working to cut capital outflows that may be heaping pressure on the value of the yuan and, late last year, moved to temporarily restrict the largest deals valued at US$10 billion or more, people familiar with the matter said at the time.

HNA's ownership is difficult to decipher as the group is held together through scores of companies - mostly unlisted entities with little available public information - holding stakes in one another. Atop the hierarchy is a person named Guan Jun, according to Chinese corporate filings.

Little is known about Guan. HNA plays down his role, with CEO Adam Tan saying he is just a Chinese businessman and chairman Chen Feng telling the South China Morning Post newspaper that Guan is not a significant shareholder as he owns only a "tiny" stake. Yet Guan owns the equivalent of a 29 per cent stake in the group, more than any of HNA's executives, including Chen and Tan's stakes combined.

HNA's ownership has also been under attack from Guo Wengui, a fugitive Chinese tycoon who has been alleging HNA has secret ties to powerful Communist Party officials - claims denied by the company. Guo is facing defamation lawsuits from HNA and others over his various claims.

Its governance has drawn questions from the likes of The New York Times, which on Wednesday reported that HNA has been doing business deals with family and friends of its top executives in the past quarter century, with limited disclosure to investors. In response to the article, HNA said its related-party transactions are reviewed and documented on terms consistent with appropriate standards.

HNA's financing practices have also stood out. Its latest annual report says the company is saddled with US$73 billion of debt, which would be the second-highest debt level for a non-financial corporation in China if HNA were to be listed, according to data compiled by Bloomberg. What is more, HNA filings show HNA and its units have pledged at least US$24 billion of shares across 15 publicly traded firms to finance its acquisitions, signalling a pattern of reliance on pledged assets that has triggered concerns from credit-rating agencies and analysts. HNA has said it has consulted financial advisers on all its pledge transactions.