WASHINGTON -- House investigators released the first transcripts from the closed-door impeachment hearings into U.S. President Donald Trump, providing new details about events at the centre of the inquiry.

In hundreds of pages, , the ousted U.S. Ambassador to Ukraine, and , a former top aide to Secretary of State Mike Pompeo, recounted mounting concerns about the administration's actions toward Ukraine, including Trump's call with President Voldymyr Zelenskiy. Democrats plan to release more transcripts in the coming days.

Takeaways from the first release on Monday:

'LOOKING TO HURT ME'

Yovanovitch told investigators she first became aware of Rudy Giuliani's involvement in Ukraine in December 2018. The ambassador knew the president's personal lawyer was interested in investigating Burisma and Joe Biden, but "it wasn't entirely clear to me what was going on."

In the months that followed, she began to understand Giuliani's work outside official diplomatic channels with Yuriy Lutsenko, who at the time was Ukraine's prosecutor general.

The core of Giuliani's involvement appears to revolve around his work with two businessmen, Lev Parnas and Igor Fruman, who were arrested and charged last month with making improper U.S. campaign contributions. They had been looking to expand their energy business in Ukraine.

She testified that she was informed by an official in Ukraine that Giuliani and Lutsenko were planning to "do things, including to me."

The businessmen, she came to understand, "needed a better ambassador" to facilitate their interests.

She was told Lutsenko "was looking to hurt me in the U.S.," adding, "I couldn't imagine what that was."

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'GO BIG OR GO HOME'

Yovanovitch said she raised concerns about the Trump administration's actions in Ukraine and the reports in U.S. media against her with Gordon Sondland, the U.S. Ambassador to the European Union. In response, he encouraged her to tweet her support for Trump on social media.

"He said, 'You know, you need to go big or go home,"' she recalled. "'You need to, you know, tweet out there that you support the president."

It was advice, she said, as a nonpartisan ambassador, "I did not see how I could implement."

At the time, some conservatives were saying that Yovanovitch had been badmouthing Trump in Ukraine, which she emphatically denied. "That allegation is false," she testified.

She was sent home.

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EARLIER TRUMP INVOLVEMENT?

The ambassador relayed being told that Trump may have joined a January 2018 phone call with Giuliani, Lutsenko and others. If true, that would directly link Trump to Giuliani's work earlier than previously understood.

Yovanovitch said she raised concerns about those and other actions to the State Department. Asked if anyone at State tried to stop the efforts, she responded: "I don't think so. I don't think they felt they could."

The career diplomat said she doesn't, "so far," fear for her safety. But she said she has been "shocked" by the administration's approach to Ukraine and was "surprised and dismayed" by what she learned from the transcript of Trump's call with Zelenskiy that sparked the impeachment probe.

On that call, Trump called Yovanovitch "bad news" and said she was "going to go through some things."

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NO SUPPORT, JUST 'BULLYING'

McKinley, the former top aide to Pompeo, detailed his frustration with Yovanovitch's ouster and his concerns about the effect that it could have on morale in the department. He said the silence from top leaders was "puzzling and baffling."

So McKinley pushed for the department to put out a statement in support of Yovanovitch. Although several other top officials agreed that it should be done, he was eventually told by a press officer that Pompeo had decided not to issue a statement. McKinley said he was told that the department didn't want to "draw undue attention to her."

McKinley said he later spoke to Yovanovitch, who told him that she would welcome a statement. She testified that he had relayed concerns from another State Department official, George Kent, who was also worried about "bullying" in the department.

McKinley testified that when he discussed the matter with Pompeo, the secretary didn't respond at all.

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POLITICIZATION OF THE STATE DEPARTMENT

McKinley said he resigned amid his concern of the increasing politicization of the department. He told Pompeo he was leaving because of his concerns over the lack of support for department employees, but he didn't name Yovanovitch directly.

"To see the emerging information on the engagement of our missions to procure negative political information for domestic purposes, combined with the failure I saw in the building to provide support for our professional cadre in a particularly trying time, I think the combination was a pretty good reason to decide enough, that I had no longer a useful role to play," McKinley told lawmakers.

McKinley said he had never seen such efforts to have the State Department dig up dirt on a political opponent.

"If I can underscore, in 37 years in the Foreign Service and different parts of the globe and working on many controversial issues, working 10 years back in Washington, I had never seen that," he said.