TAIPEI, Taiwan — It was the ultimate success story of China Inc. 2.0: A private-sector technology start-up became an Internet juggernaut that conquered the Chinese market and set its sights on the world.

But like in the folk tale, Alibaba first struck gold — and then met trouble.

Chinese regulators announced a multipronged antitrust investigation Thursday into its most successful Internet company, making moves that could potentially break up Alibaba’s sprawling e-commerce business or splinter its highly lucrative financial services affiliate.

While it has grown into the dominant player in Chinese online shopping — now raking in $50 billion a year in revenue — Alibaba in the past decade has steadily encroached on China’s tightly controlled financial sector through its Ant Group spinoff. Ant Group, a $16 billion-a-year business, has been chipping away at powerful state banks’ market share and unnerving regulators with investment and lending products that have become so popular that Ant sometimes acts as a lender to government banks — not the other way around.

The companies have amounted to a vast, loosely linked conglomerate under the control of the billionaire Jack Ma, China’s richest man, that could challenge the state itself.

On Thursday, the state fought back. China’s State Administration for Market Regulation said it would look into complaints from online merchants about Alibaba’s demands for exclusivity deals. In a simultaneous announcement, banking regulators said they were summoning Ant Group executives for discussions about the financial platform’s competitive and consumer protection practices.

It was a humbling turn for Ma, a self-made billionaire who was once celebrated as a symbol of China’s entrepreneurial spirit.

“It’s political, and it’s not political,” said Andrew Kemp Collier, managing director of Orient Capital Research in Hong Kong. “There are genuine worries about an online financial sector that’s not adequately regulated, which every country has struggled with, but there’s also a concern that state banks that are the heartbeat of China’s economy will start to be second-class citizens to Alibaba.”

Thursday was the culmination of months of tension between Ma and leaders in Beijing. In October, Ma ruffled feathers by telling a technology conference that Chinese financial regulators stifle innovation and dismissing big state banks as “pawnshops.”

Weeks after, regulators nixed at the 11th hour Ant’s $34 billion initial public offering, the largest in history, and summoned Ma for urgent meetings. State media coverage of the celebrity entrepreneur turned icy. Ma hasn’t been seen in public since October.

“It’s absolutely true that Beijing is nervous about any private company getting too big for its britches,” Collier said.

Alibaba and Ant swiftly announced Thursday that they would cooperate fully with the government. “We will seriously study and strictly comply with all regulatory requirements and commit full efforts to fulfill all related work,” Ant Group said in a statement. Alibaba said it would actively cooperate with the probe and business operations would carry on normally.

Alibaba shares in Hong Kong plummeted nearly 8 percent. The company also trades on the New York Stock Exchange.

Beijing’s moves reflect a long-standing concern about the concentration of power held by modern Internet companies — a sentiment echoed on Capitol Hill. Chinese policymakers have also warned for years that the entire economy could get dragged down by rampant borrowing.

Moreover, the financial sector is particularly sensitive for China’s leaders because state banks and the loans they generate are levers for the government to steer economic growth according to its centrally planned trajectory. Weakened state banks could undermine Beijing’s grip on industrial policy.

The Ant Group started a decade ago as Alipay, the escrow and money-transfer service that people used to pay for goods on Alibaba’s e-commerce platforms. The company offered far higher interest rates on deposits compared to state banks, and began offering loans.

By the end of the decade, it was morphing into a behemoth offering money management and investment services, and a platform for crowdfunding. Small local banks struggling for deposits often used Ant’s online presence as a platform to attract customers or raise cash.

This month, Guo Shuqing, chairman of China’s Banking Regulatory Commission, didn’t name Ant but warned explicitly that a few Internet-based financial technology services were adopting a “winner-takes-all” market approach and becoming “too big to fail,” posing risks to the Chinese economy. Consumers, abetted by smartphone-based lending schemes, were also borrowing too easily and spending too much, Guo said.

In November, regulators announced a draft version of stricter anti-monopoly laws targeting Internet companies, while the Communist Party Politburo said this month the country needed to prevent “disorderly capital expansion.”

The crackdown on Alibaba also aligns with the ideological outlook of Chinese President Xi Jinping, a committed Marxist-Leninist who has advocated firmer Communist Party control over every aspect of society. Xi has doubled down on support for state companies, often at the expense of private businesses.

State firms “form the economic and political foundation of China’s socialist system and are a key pillar of party rule,” Xi told officials in an internal speech in April. “They must be built stronger, bigger and better.”

Since Xi took power, lending patterns by state banks have flipped, with the majority of credit now going to state companies rather than the private sector, according to research by Nicholas Lardy of the Peterson Institute for International Economics.

Private conglomerates like Anbang Insurance and the HNA Group have been forced to sell off overseas assets, while highflying Internet companies like Tencent, the Alibaba competitor and developer of WeChat, have encountered regulatory trouble when they expand into new areas like music streaming and credit reporting.

Xi personally ordered regulators to examine Ant, the Wall Street Journal reported this month.

Some Communist Party mouthpieces took the opportunity Thursday to point out that big tech has run amok and was undermining social values by lending to young people.

Financial innovation has been “distorted by greedy capital,” said China Comments, an online outlet commissioned by the party’s propaganda department. “Although Internet platforms are mostly operated by private entities, they are de facto public products. A monopoly harms livelihoods.”