Top Democrats in Congress want the FBI to investigate a Chinese American business executive accused of using her access to President Trump to facilitate opportunities for Chinese executives, activities that came to light after a Florida massage parlor she founded was linked to a sex trafficking and prostitution ring.

In a letter to the heads of the FBI, national intelligence agencies and Secret Service, the top Intelligence and Judiciary committee Democrats in the Senate and House asked for investigations into “credible allegations of potential human trafficking, as well as unlawful foreign lobbying, campaign finance and other activities” by Li “Cindy” Yang, a naturalized U.S. citizen from China.

Yang, a Republican donor, has made frequent visits to Trump’s Mar-a-Lago Club and attended the president’s Super Bowl party this year, snapping a selfie with the president during the event.

It is that level of contact — though it appears that Yang often had to pay her way into events — that has congressional investigators concerned that her activities “could permit adversary governments or their agents access to these same politicians to acquire potential material for blackmail or other even more nefarious purposes.” They acknowledged, however, that Yang may not have had such compromising intentions and that her “activities may only be those of an unscrupulous actor allegedly selling access to politicians for profit.”

Evan W. Turk, an attorney for Yang, said a legal team has reviewed the allegations, which he described as “politically driven.”

“We have seen the Democratic partisan letter and allegations. Our firm will represent our client and her interest as an American through any developments in this case. It seems [like] another politically driven expedition. We will be addressing these matters when appropriate,” Turk said in a statement to The Washington Post.

The FBI, the director of national intelligence, the Secret Service and the White House all declined to comment. The letter’s authors requested a response by the close of business Thursday.

The effort was endorsed by House Speaker Nancy Pelosi (D-Calif.) and Senate Minority Leader Charles E. Schumer (D-N.Y.), who in a joint statement Monday said “the facts in this situation are very concerning” and urged the FBI “to adhere to the joint bicameral requests . . . and start an investigation.”

Yang founded a chain of Florida spas and massage parlors, including Orchids of Asia, the establishment where New England Patriots owner Robert Kraft was accused of soliciting prostitution in a recent sting. Kraft has pleaded not guilty.

Although Yang has not been charged in that investigation — and sold the day spa in question six years ago, her lawyer said — the episode has increased scrutiny of her other businesses, at least one of which congressional investigators worry could pose national security concerns.

Yang operates a company called GY US Investments, which offered prospective clients a chance to rub elbows with Trump and other powerful politicians through dinners, fundraisers and other events — including at Mar-a-Lago. In one instance in late 2017, the Miami Herald reported, Yang boasted of bringing a group of Chinese executives to a fundraiser in New York — which is legal as long as they were guests and didn’t reimburse Yang for their entry. Democrats suspect, however, that they might have.

In the Democrats’ letter, Sens. Mark R. Warner (Va.) and Dianne Feinstein (Calif.) and Reps. Adam B. Schiff (Calif.) and Jerrold Nadler (N.Y.) asked whether Yang or others were “offering foreigners access to the President, those close to him, or other senior officials in exchange for money” — and if the Trump campaign was doing a thorough job to ensure that the funds weren’t “being contributed illicitly or through straw donors.”

They also asked whether Yang or her clients had violated foreign lobbying laws — and whether her actions had brought her to the attention of law enforcement, whether for her business ties, national security concerns or human trafficking.

Michelle Ye Hee Lee and Ellen Nakashima contributed to this report.