▶ Watch Video: New details in Hunter Biden federal investigation

The federal investigation into Hunter Biden’s business practices is broader than previously known, with multiple sources telling CBS News the probe is exploring whether the younger Biden and his associates violated tax, money laundering and foreign lobbying laws.

Business records reviewed by CBS News and documents released by Republicans in Congress indicate Hunter Biden and his firm were involved in multiple financial transactions with a Chinese energy company called CEFC. Republicans allege that the company is an arm of the Chinese government.

In 2017, the year after Joe Biden left the vice presidency, an official with the Chinese energy company signed a $1 million retainer for Hunter Biden’s services as a lawyer.

The new client, CEFC official Patrick Ho, was later convicted on unrelated international bribery and money laundering charges for work in Africa.

This week on the Senate floor, Republican Chuck Grassley presented financial records the Senate obtained that he said showed six-figure payments from the Chinese energy company to Hunter Biden’s firm, which included President Biden’s brother James Biden.

“Hunter Biden and James Biden served as the perfect vehicle by which the Chinese government could gain inroads here in the United States,” Grassley said.

An attorney for Hunter Biden did not respond to CBS News’ request for comment. CBS News was unable to reach a representative for James Biden for comment. Last year, Hunter Biden told CBS News correspondent Anthony Mason the president did not financially benefit, directly or indirectly, from his business ventures.

Attention on Hunter Biden’s foreign business dealings has re-emerged as a political issue in recent days. Questions about then-candidate Biden’s son reached a fever pitch during the 2020 campaign. After the election, the White House left the Trump-appointed federal prosecutor in Delaware in place — White House officials said to avoid any suggestion they were meddling in the probe.

Earlier this month, White House press secretary Jen Psaki said any answers to questions about the investigation would have to come from the Justice Department or Hunter Biden’s representatives.

“I’m a spokesperson for the United States,” Psaki added. “He doesn’t work in the government.”