Jason Lee/Reuters

For more than a decade, Wall Street’s biggest banks have hired the sons and daughters of senior Chinese government officials in the hopes that they can open doors and secure deals in the world’s fastest-growing major economy.

The hirings were not well publicized, but they were no secret. The grandson of former Chinese President Jiang Zemin once worked for Goldman Sachs; the daughter of former Prime Minister Wen Jiabao used to work for Credit Suisse; and in 2006, the son-in-law of Wu Bangguo, then a member of the Politburo of the Communist Party, helped Merrill Lynch win a deal to arrange a $22 billion listing of the state-owned banking giant I.C.B.C.

While Wall Street may be familiar with the recruiting of the children of China’s political elite, a new Securities and Exchange Commission investigation has raised the question of whether hiring the children of officials of state-controlled companies crosses a line. The S.E.C. is examining whether JPMorgan Chase tried to win business in China by hiring the children of two senior Chinese officials, in possible violation of American anticorruption statutes.

The focus of the investigation, first disclosed by The New York Times on Sunday, has prompted a scramble among the Hong Kong rivals of the New York bank to assess the potential risks of their own hirings. JPMorgan has not been accused of any wrongdoing and has said it is cooperating with the inquiry.

Many of the major banks declined to comment. But in a series of interviews, bankers and lawyers said the practice of hiring the children of government officials was so widespread that banks competed to see who could hire the most politically connected recent college graduates.

“If you don’t have any of them, you may be at a disadvantage,” said Jeffrey Sun, a lawyer at Orrick, Herrington & Sutcliffe who is based in Shanghai. “For international banks, if you don’t have any of them, it’s difficult for you to get into the circle. You need intelligence. You need access to information. And this is one way to get that. Even though it’s an ‘inconvenient fact’ for most Chinese like me, that’s real life.”

The recruitment of the children of China’s elite has gone on even as Wall Street banks in China have reined in other practices.

In recent years, United States authorities have stepped up enforcement of the Foreign Corrupt Practices Act, which essentially prohibits American companies from giving “anything of value” to a foreign official to win “an improper advantage” in business. As a result, bank employees are usually restricted from paying for the travel, meals or entertainment of Chinese officials.

“I can’t even take a Hong Kong official to a rugby match,” complained one Hong Kong banking employee, who asked not to be named. “It’d be considered a bribe.”

But the investment banks continued to compete to hire the sons and daughters of senior Chinese officials because the practice was considered less risky and was rarely prosecuted, legal experts and Hong Kong bankers say.

Although many of those hired have worked diligently, others have been placed on the payroll with little or no work expected of them.

“Some of them never even come into the office,” said one Hong Kong banker. “But everyone does it. We have lost business as a direct result of some state-owned company boss placing a kid at our rival.”

The practice has flourished partly because there seemed to be a good defense, legal analysts say. Banking is a relationship business, and for global companies, hiring well-connected individuals occurs around the world.

Also, many of the children of senior Chinese officials who get jobs with the major banks are highly educated, with degrees and M.B.A.’s from the world’s top universities.

There is another reason, analysts say, that major Wall Street banks hire this way: proving an investment bank won a deal because of hiring just one individual would be a challenge for regulators in the United States.

“Banks all over the world hire well-connected people to build existing relationships,” said David M. Webb, a former investment banker who is now a corporate governance expert based in Hong Kong. “It’ll be hard to prove there’s a direct connection” to the banks’ winning a particular deal, he said.

Why American authorities are now beginning to look at the hiring of the sons and daughters of senior leaders — the so-called princelings — is unclear.

Most China-related cases previously brought by the S.E.C. and the Justice Department have involved global companies accused of bribing Chinese officials with gifts, entertainment and travel junkets. In 2007, Lucent settled with the Justice Department over the financing of 315 trips for Chinese government officials to Las Vegas, Disneyland and Universal Studios, among other stops.

In the case of JPMorgan, the S.E.C. has begun a civil inquiry into whether the bank violated United States antibribery laws when its Hong Kong office hired the son of Tang Shuangning, chairman of the state-owned China Everbright Group, and the daughter of the deputy chief engineer of China’s Ministry of Railways, according to a confidential government document reviewed by The New York Times, as well as public records.

After the two were hired, JPMorgan won deals with the China Everbright Group and the China Railway Group, which operated under the influence of the railway ministry. The ministry was broken up this year after a series of corruption scandals.

In a statement on Monday, the China Everbright Group denied there was any wrongdoing when it selected JPMorgan.

The background of the railway official and his family is intriguing.

JPMorgan brought on Zhang Xixi, a Stanford graduate and the daughter of Zhang Shuguang, in 2007. She has since left the bank. Her father, the former deputy chief engineer at the railway ministry, was detained in 2011 on corruption accusations. To date, he has not been prosecuted.

According to records reviewed by The Times, the Zhang family owned a $1 million home in Walnut in Southern California, even though Chinese government officials rarely earn more than $15,000 a year.

Still, United States investigators will need to prove that in hiring Ms. Zhang, JPMorgan directly won business influenced by her father.

“These cases will need to be built on a lot more than simply the fact that a bank hired the relative of a party official,” said William F. McGovern, a former S.E.C. official who is now with the New York law firm Kobre & Kim.

Government investigators, he said, “are likely trolling through internal e-mails and transaction records to find evidence that the hire was part of a corrupt exchange of favors for business. That is no easy task.”

If investigators do turn up evidence that JPMorgan won investment banking business in China directly related to the hiring of the children of two officials, it could shake up the world of finance here in China.