Elijah Cummings. MSNBC

The top Democrat and ranking member on the House Committee on Oversight and Government Reform sent a letter to US Secret Service director Randolph D. Alles on Monday requesting any documents related to vetting who came and went from Trump Tower on June 9, 2016.

Cummings wrote that the letter was prompted by "recent conflicting reports" on the Secret Service's role in vetting Russian lawyer Natalia Veselnitskaya, former Soviet military intelligence officer Rinat Akhmetshin, and others who met with Donald Trump Jr., Trump son-in-law Jared Kushner, and former campaign manager Paul Manafort at Trump Tower in June 2016.

Cummings was referring to President Donald Trump's lawyer's assertion Sunday that the meeting between the president's son, top campaign staff, and a lawyer who's been described as a "Russian government attorney" was innocent. If it weren't, he said, the Secret Service would not have let the Russians into Trump Tower.

"Well, I wonder why the Secret Service, if this was nefarious, why the Secret Service allowed these people in," one of Trump's lawyers, Jay Sekulow, said on ABC's "This Week."

"The president had Secret Service protection at that point, and that raised a question with me," Sekulow added.

But the Secret Service released a statement the same day confirming that Trump Jr. was not under its protection on June 9, 2016. The agency said it "would not have screened anyone he was meeting with at that time." Neither Kushner nor Manafort were under Secret Service protection at that point.

Cummings' letter noted that the meeting has been said to have taken place on the floor beneath the one Trump occupied during the campaign. Trump had just clinched the Republican nomination at the time, and he was also under Secret Service protection.

Trump has denied knowledge of the meeting. But it emerged last week that Trump himself had signed off on Trump Jr.'s initial statement regarding his interaction with Veselnitskaya, which was amended several times as new details about the meeting continued to spill out.

It was also reported Saturday that the Trump reelection campaign made a $50,000 payment to Trump Jr.'s lawyer, Alan Futerfas, in June. The payment was made weeks before reports on Trump Jr.'s meeting with Veselnitskaya, Akhmetshin, and others.