The whistleblower whose complaint about a phone call between President Trump and his Ukrainian counterpart triggered an impeachment inquiry reportedly is a CIA officer who was detailed to the White House.

The New York Times, quoting three people familiar with the person’s identity, reported the whistleblower has returned to the CIA.

The complaint, released Thursday before testimony by Acting Director of National Intelligence Joseph Maguire, raises concerns about a July 25 call between Trump and Ukraine President Volodymyr Zelensky in which Trump reminds his counterpart of past U.S. help and then asks for a favor, according to a reconstructed White House transcript. Days before the call, Trump withheld nearly $400 million in military aid designed to fight Russian aggression, but he did not explicitly link release of the aid to a request that Zelensky help investigate former Vice President Joe Biden, a 2020 presidential contender.

The whistleblower said he spoke with “a half dozen U.S. officials” during a four-month period who described events that prompted deep concern.

“I have received information from multiple U.S. government officials that the president of the United States is using the power of his office to solicit interference from a foreign country in the 2020 U.S. election,” the complaint reads. “This interference includes, among other things, pressuring a foreign country to investigate one of the president’s main domestic political rivals.”

The whistleblower said he was not present for the call but was among those who received a readout. Subsequent conversations with some of the dozen people who listened in revealed deep concern the president had abused “his office for personal gain.”

The complaint said it appeared the White House tried to hide all records of the call and expressed concern over whether campaign finance violations had been committed. Concern also was expressed over the role of Trump attorney Rudy Giuliani, who served as a go-between for messages between Trump and Ukrainian officials, and over Attorney General William Barr’s role.

The Times said the whistleblower complaint indicates it was written by someone trained as an analyst well acquainted with U.S. foreign policy toward Europe and with a deep understanding of Ukrainian politics and some knowledge of the law.

Attorney Andrew Bakaj, who is representing the whistleblower, declined to confirm whether his client works for the CIA.

Trump disparaged the whistleblower and called the House investigation a “Democrat scam.”

“A whistleblower with secondhand information? Another fake news story!” Trump tweeted.

Before leaving New York where he attended the U.N. General Assembly meeting, Trump characterized whoever gave information to the whistleblower as "close to a spy" and possibly guilty of treason.

“I want to know who’s the person who gave the whistle-blower the information because that’s close to a spy,” Trump said. “You know what we used to do in the old days when we were smart with spies and treason, right? We used to handle it a little differently than we do now.”