New potential whistleblowers are coming forward to the House Democrats’ impeachment inquiry, two congressional sources tell The Daily Beast.

They seem to be emboldened by the actions of the whistleblower whose explosive account of President Donald Trump’s phone call to Ukraine’s Volodymyr Zelensky about investigating Trump’s domestic political rivals ignited the impeachment inquiry. Another whistleblower is known to have come forward.

Congressional investigators are currently vetting the new accounts they’ve received for credibility. Accordingly, knowledgeable sources would not discuss where in the government these new would-be whistleblowers come from, nor what they purport to have to say.

It’s also unknown if their accounts are as significant as that of the intelligence whistleblower whose alarm over President Trump’s July 25 phone call sparked the impeachment probe. Investigators often encounter cranks as well as those with genuine knowledge of wrongdoing. Nor is it clear if these new ostensible whistleblowers have contacted any inspectors general, as the original two whistleblowers did.

“There are clearly numerous whistleblowers out there and many people who possess firsthand relevant information who could come forward, and I expect some will,” said attorney Mark Zaid, who represents those two whistleblowers (and also represents The Daily Beast in freedom-of-information lawsuits).

One knowledgeable source said that the daily accumulation of revelations about Trump’s willingness to use U.S. foreign relations for his personal political benefit has prompted more people to approach Congress. Two associates of Trump attorney Rudy Giuliani have been arrested and charged with campaign-finance violations arising from their Ukraine dirt-digging effort. The Financial Times reported that Trump China adviser Michael Pillsbury said he received “quite a bit of background” on Joe Biden’s son after Trump publicly called for China to aid his domestic political prospects. The Washington Post reported that Giuliani, a former federal prosecutor, and Trump attempted to quash a prosecution of a Turkish national—represented by Giuliani and important to Turkish President Recep Tayyip Erdogan—for violating Iran sanctions.

Investigators are using the soon-to-expire congressional recess to vet the accounts they’re getting.

Rep. Adam Schiff (D-CA), who chairs the House Intelligence committee, a locus of the impeachment probe, told The Daily Beast this month that he did not want to comment on whether investigators had heard from additional whistleblowers. Schiff noted that his committee rarely acknowledges receiving whistleblower complaints because “people can reverse-engineer who whistleblowers are” given an abundance of identifying information.

“The only thing I can say, and I don’t want to suggest too much by this, is we began discussions with other committees investigating these issues, when the first news started breaking about Giuliani seeking foreign help in Ukraine to aid the president’s campaign,” Schiff said.

The revelations come while Congress interviews the U.S. ambassador to Ukraine the administration removed, Maria Yovanovitch, despite the White House’s announced refusal to cooperate with the House Democratic inquiry. Other cracks in that front have emerged. On Friday, Gordon Sondland, the U.S. ambassador to the European Union implicated in the Ukraine pressure campaign, announced through his lawyers that he will defy State Department instructions against talking to Congress.