(CNN) —  

Two Democratic lawmakers sent a letter to President Donald Trump on Friday criticizing the administration’s response to Saudi journalist Jamal Khashoggi’s disappearance and asking for information about what they describe as the President’s “ongoing personal enrichment from Saudi government payments.”

The letter, signed by Democratic Sen. Richard Blumenthal of Connecticut and Rep. Jerrold Nadler of New York, accuses the President of giving “undue credence to the Saudi government’s unbelievable stories and denials,” and states, “Your administration’s response calls into question whether you are acting based on the American public’s interests or your own private interests.”

In light of that, the lawmakers say they are writing “to request additional information about your ongoing personal enrichment from Saudi government payments.”

Hoping to win back the majority in the US House of Representatives after this fall’s midterms, Democrats have already signaled plans to open investigations into Trump’s tax returns, business interests, Cabinet secretaries and whether there was any collusion between Russia and the Trump campaign. The letter signals a new vein Democrats intend to mine, opened up by the Saudi crisis.

Nadler told CNN Friday that the Democrats will subpoena business records if they take control of the House.

CNN has reached out to the White House and the Trump Organization for response to the letter from congressional Democrats.

The President has recently shifted his tone on the fate of the journalist who went missing after going to the Saudi consulate in Istanbul, Turkey, more than two weeks ago. The President said for the first time on Thursday that he believes Khashoggi is no longer alive.

But Trump has appeared reluctant to directly blame the Saudi government. Instead, he has repeated denials from the Saudi Arabian Crown Prince who has denied any knowledge of what happened. Trump has even floated – without evidence – the possibility that the disappearance could have been the work of “rogue killers.”

Republicans and Democratic lawmakers have put pressure on the administration to determine what took place and take punitive measures in response. That pressure has continued this week, with some Republican lawmakers calling for sanctions against the Saudis if it is determined that they were responsible.

The letter from Blumenthal and Nadler outlines a series of questions that they want answered, saying that there is “widespread concern” that the President’s “receipt of foreign emoluments from the Saudi Arabian government may be influencing the manner in which your Administration is responding to the horrific killing of Jamal Khashoggi.”

Trump’s financial ties with the Saudis date back to the 1990s.

When one of his casino projects was faltering under a mountain of debt, a Saudi prince bought Trump’s yacht for $20 million. Ten years later, public records show Trump sold the 45th floor of his Trump World Tower in New York to the Kingdom for millions of dollars.

More recently, since Trump took office, his hotels have benefited from Saudi business. Between October 2016 and March 2017, a Saudi lobbying firm paid Trump’s Washington, DC, hotel more than $270,000 for food and accommodations. Revenue at Trump’s Manhattan hotel on Central Park West increased during the first quarter of 2018 — in part because of a visit from Saudi Crown Prince Mohammed Bin Salman, according to a letter obtained by The Washington Post. In the letter, the Hotel’s general manager wrote that Bin Salman didn’t stay at the hotel himself but “due to our close industry relationships, we were able to accommodate many of the accompanying travelers.”

One of the questions in the letter sent to the President Friday asks what percentage of revenue at certain Trump Organization properties “can be attributed to foreign government patronage.”

The Trump Organization says it’s donating foreign profits but Nadler told CNN that payments from foreign governments are altogether problematic from an ethics standpoint — whether or not there’s a profit associated with the payment.

“If the Saudis rent a certain number of rooms and prevent a Trump Hotel from losing money, that’s a benefit to the President,” Nadler told CNN.

The letter states, “Press reports indicate that, in 2018, there has been significant foreign government patronage at the Trump International Hotel in Washington, D.C., the Trump International Hotel & Tower in New York City and in Chicago, and Mar-a-Lago in Palm Beach, Florida.”

It asks, “what percentage of the revenue at these Trump Organization properties can be attributed to foreign government patronage? Please identify the specific property; the foreign government patron; and the amount of revenue generated from each foreign government.”

Another question asks, “Are there other Trump Organization properties that have derived revenue from foreign government patronage?”

Blumenthal also signed onto another letter to the President earlier in the week sent by a group of Senate Democrats. That letter asked Trump to disclose information related to “financial ties between the Kingdom of Saudi Arabia and your family business interests.”

CNN’s Bard Wilkinson contributed to this report.