HONG KONG — A Chinese online finance company bilked investors out of more than $7.6 billion, spent lavishly on gifts and salaries, and buried the evidence, according to local authorities who described the operation as an enormous Ponzi scheme.

The accusations throw a shadow over China’s online finance industry, a lucrative area for many global leaders in the sector, but one that authorities say has also drawn a growing number of cases of fraud and flameouts.

Chinese officials say that the online company, Ezubao, once a dynamo of the industry, offered mostly fake investment products to its nearly 1 million investors, according to the state-run Xinhua news agency. Authorities arrested 21 people in Anhui, the eastern Chinese province where Ezubao is based, and closed some of the platform’s operations, the agency reported.

“Ezubao is a Ponzi scheme,’’ Xinhua quoted Zhang Min, a former executive at the company, as saying.

Officials at the company could not be reached for comment.

A new category of Chinese companies has emerged in recent years to do for customers what the country’s state-owned banks will not. Chinese customers widely use their smartphones to buy groceries or transfer money, and new types of finance companies are offering loans to small businesses, students, and others that state banks traditionally ignore.

Ezubao claims to be a peer-to-peer lender, which matches investors with potential borrowers over the Internet. China’s growth in peer-to-peer lending has been strong, and Morgan Stanley estimated total volume in the country last year at $33.2 billion, surpassing the United States. The Chinese market is highly fragmented, Morgan Stanley says, with more than 1,500 such lending platforms.

But cases of illegal fundraising related to peer-to-peer lending have grown quickly in the past two years, according to the local authorities, and officials pledged in December to tighten regulation of the industry.

Because of the enormous sums involved and the large investor base, the collapse of a major online-financing platform could raise concerns over confidence in the security of such investments.

Ezubao has been under official scrutiny for weeks. In December, Xinhua said the company was under investigation for suspected illegal business activities.

On Sunday, Xinhua said an investigation by local authorities had found that most of the investment products the company marketed were fake. Some offered investors annual interest payments of as much as 15 percent.

In reality, the platform, which was set up by the Yucheng Group in July 2014, was used to enrich top executives, Xinhua said.

That included around $150 million that Ding Ning, chairman of Yucheng, is reported to have spent on items and gifts including real estate, cars, and luxury goods, according to the report.

The report added that the salary paid to Ding’s brother, Ding Dian, was increased from about $2,800 a month to $150,000 a month. The company spent as much as $120 million on payroll in the month of November.

Another executive, who was in charge of risk management at a company affiliated with the Yucheng Group, said that more than 95 percent of the investment products that Ezubao marketed on the platform were fake, according to the report, and those responsible went to considerable lengths to conceal their ruse.

The Xinhua report said that suspects had placed about 1,200 documents and other pieces of evidence related to the scheme in 80 bags and had buried them nearly 20 feet underground at a site on the outskirts of Hefei, the capital of Anhui province.

It took the police 20 hours with two excavators to unearth the evidence, Xinhua said, and the police described the case as “extremely difficult.’’