Republican presidential nominee Donald Trump walks on stage during a campaign event in Dimondale, Michigan, U.S., August 19, 2016. REUTERS/Carlo Allegri A New York Times investigation into Republican presidential nominee Donald Trump's US real-estate holdings revealed that companies he owns have at least $650 million in debt — twice the amount that Trump's public filings, made as part of his campaign, show.

Trump's dealings also depend on a variety of sources, one of which he has repeatedly attacked during his campaign: China, The Times found.

Aside from revealing more information about Trump's complex business web, the investigation also shed light on how much remains "shrouded in mystery," according to The Times, as well as the potential shortcomings of the Federal Election Commission's (FEC) financial-disclosure form for candidates.

Among the specifics, The Times reports that:

An office building in Manhattan, which Trump partly owns, carries a $950 million loan, partially overseen by the Bank of China, one of the largest in the country.

A "substantial portion" of Trump's wealth stems from three partnerships that owe another $2 billion. While Trump may not be held personally liable if the loans went into default, the value of his investments would drop.

In 2015, Trump borrowed $160 million from Ladder Capital, a small New York firm, which his financial-disclosure form simply lists as valued at more than $50 million.

The publication found three instances where Trump had ownership interest in a building but did not disclose the related debt. Of these investments, one again involves a partial loan from the Bank of China.

While the full terms of Trump's partnerships remain unknown, loans connected with them reach $1.95 billion, according to various public documents cited by The Times. The Trump Organization's chief financial officer Allen Weisselberg, however, told The Times that neither Trump nor the company was responsible for these debts.

The Times notes that the fact that the publication found a substantial increase in debt relates more to what the FEC form asks of candidates rather than any fault of Trump. The form requires candidates disclose their assets and debts in ranges up to $50 million, instead of precise numbers.

In late July, the FEC released a 92-page personal-financial-disclosure report for the real-estate mogul turned politician. While the report still didn't completely detail Trump's supposed wealth, a statement released by the campaign claimed it would reveal a "massive" net worth "in excess of" $10 billion.

Weisselberg also told The Times that debts for properties where a Trump company owned less than a 100% stake were not disclosed on the form.

For the investigation, The Times partnered with national property-information firm RedVision Systems to search publicly available data on more than 30 US properties, identified through Federal Election Commission (FEC) filings and information provided by Trump, like filings with the Securities and Exchange Commission (SEC).

Although the investigation covered a variety of documents and records, The Times concentrated on commercial holdings, such as office towers, golf courses, residential properties, and other endeavors, but exempted Trump's businesses outside the US.

Aside from skepticism and controversy over Trump's net worth and debts, the nominee has recently come under fire for refusing to release his tax returns. Most Republican nominees over the past several decades have released the same information, according to the Tax History Project.