WASHINGTON (AP) — A House committee chairman said his panel will investigate what he says are "profoundly alarming" text messages that have raised questions about the possible surveillance of former Ambassador to Ukraine Marie Yovanovitch before she was ousted by the Trump administration last spring.

House Democrats on Tuesday night released a trove of documents they obtained from Lev Parnas, a close associate of President Donald Trump's personal lawyer, Rudy Giuliani. The messages show that a Trump donor named Robert F. Hyde disparaged Yovanovitch in messages to Parnas and gave him updates on her location and cellphone use.

Rep. Eliot Engel, a New York Democrat who chairs the House Foreign Affairs Committee, said Wednesday that the messages are "profoundly alarming" and "suggest a possible risk" to Yovanovitch's security in Kyiv before she was recalled from her post.

"These threats occurred at the same time that the two men were also discussing President Trump's efforts, through Rudy Giuliani, to smear the ambassador's reputation," Engel said.

He said the committee staff flagged the information for the State Department's Bureau of Diplomatic Security and is seeking assurances that proper steps have been taken to ensure the security of Yovanovitch and committee staff. He said he also wanted to know what, if anything, the State Department knew about the situation.

"This unprecedented threat to our diplomats must be thoroughly investigated and, if warranted, prosecuted to the fullest extent of the law," Engel said.

Democrats released the files Tuesday as they prepared to send articles of impeachment to the Senate for Trump's trial. The documents add new context to their charges that Trump pressured Ukraine to investigate Democrats as he withheld military aid.

They show Parnas communicating with Giuliani before Yovanovitch's removal, and that he appeared to be pushing unfounded claims that Democrat Joe Biden and his son, Hunter Biden, were somehow engaged in corruption in Ukraine. The documents include a handwritten note that mentions asking Ukraine's president to investigate "the Biden case."

Among the documents is a screenshot of a previously undisclosed letter from Giuliani to Ukrainian President Volodymir Zelenskiy dated May 10, 2019, which was before Zelenskiy took office. In the letter, Giuliani requests a meeting with Zelenskiy "as personal counsel to President Trump and with his knowledge and consent."

One of the documents is a handwritten note on stationery from the Ritz-Carlton Hotel in Vienna that says "get Zalensky to Annonce that the Biden case will be Investigated." Trump asked Zelenskiy in a July 25 call to investigate the Bidens. Hunter Biden served on the board of a gas company based in Ukraine.

Democrats said Parnas' attorney confirmed that Parnas wrote the notes.

The documents — including phone records, texts and flash drives turned over by Parnas — were sent to the House Judiciary Committee by three other House panels "to be included as part of the official record that will be transmitted to the Senate along with the Articles of Impeachment," according to a statement. Some of the materials were made public while others were marked as sensitive.

Parnas and his business partner, Igor Fruman, both U.S. citizens who emigrated from the former Soviet Union, were indicted last year on charges of conspiracy, making false statements and falsification of records. Prosecutors allege they made outsize campaign donations to Republican causes after receiving millions of dollars originating from Russia. The men have pleaded not guilty.

In several of the documents, Parnas communicated with Giuliani about the removal of Yovanovitch. The ambassador's ouster, ordered by Trump, was at the center of the Democrats' impeachment inquiry. Yovanovitch testified in the House impeachment hearings that she was the victim of a "smear campaign."

Trump on the July call told Zelenskiy that Yovanovitch was "going to go through some things." She had been recalled from her diplomatic post roughly three months earlier.

On April 23, just before Yovanovitch was directed to return to the United States, Giuliani texted Parnas, "He fired her again." Parnas texted back, "I pray it happens this time I'll call you tomorrow my brother."

Parnas also received messages from Hyde, who referred to Yovanovitch as a "bitch." Hyde is now running for a U.S. House seat in Connecticut.

After texting about the ambassador, Hyde gave Parnas detailed updates that suggested he was watching her. In one text, Hyde wrote: "She's talked to three people. Her phone is off. Her computer is off." He said she was under heavy security and "we have a person inside."

Hyde at one point texted Parnas that ''they are willing to help if we/you would like a price," and "guess you can do anything in Ukraine with money ... is what I was told."

Parnas texted back: "lol."

Lawrence Robbins, an attorney for Yovanovitch, called for an investigation into the messages.

"Needless to say, the notion that American citizens and others were monitoring Ambassador Yovanovitch's movements for unknown purposes is disturbing. We trust that the appropriate authorities will conduct an investigation to determine what happened."

On Twitter, Hyde dismissed the claims as "laughable" and appeared to try to distance himself from Parnas. He said he would "welcome" an investigation.

The text messages show that Parnas consulted Giuliani in January 2019 after the U.S. denied a visa to former Ukrainian Prosecutor General Viktor Shokin. Giuliani replied: "I can revive it."

The following day, Giuliani told Parnas: "It's going to work I have no 1 in it." Giuliani then predicted "he will get one," before giving Parnas the phone number for Jay Sekulow, the leader of the president's personal legal team. Sekulow is expected to be part of Trump's legal team during the impeachment trial.

A federal judge earlier this month ruled that Parnas could provide the materials to Congress as part of the impeachment proceedings.

Democrats voted in December to impeach Trump for abuse of power and for obstruction of Congress.

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Associated Press writers Michael Balsamo, Lisa Mascaro and Zeke Miller contributed to this report.