Washington (CNN) Secretary of State Mike Pompeo maintained a persistent silence for more than 48 hours after stunning new evidence emerged suggesting the former ambassador to Ukraine may have been illegally surveilled before she was forced out of her job by President Donald Trump.

Pompeo finally addressed the matter on Friday morning in an interview with conservative radio host Hugh Hewitt saying that, "to the best of (his) recollection," he was not aware that former US Ambassador to Ukraine Marie Yovanovitch may have been monitored at the behest of associates of the President's personal lawyer Rudy Giuliani.

"Until this story broke, I had, to the best of my recollection, had never heard of this at all," Pompeo told "The Hugh Hewitt Show."

Pompeo also denied knowing indicted Giuliani associate Lev Parnas, who provided the texts that suggested the possible monitoring of Yovanovitch.

In a separate interview on Friday, the top US diplomat publicly committed to look into the possible surveillance -- more than 24 hours after Ukraine announced it had launched a criminal probe into the matter.

"We will do everything we need to do to evaluate whether there was something that took place there," Pompeo told conservative radio host Tony Katz.

"I suspect that much of what's been reported will ultimately prove wrong, but our obligation, my obligation as secretary of state, is to make sure that we evaluate, investigate. Any time there is someone who posits that there may have been a risk to one of our officers, we'll obviously do that," Pompeo said.

Pompeo did not offer words of support for Yovanovitch personally, but told Tony Katz that "it is always the case at the Department of State that we do everything we can to ensure that our officers, not only our ambassadors but our entire team, has the security level that's appropriate."

Pompeo came into the role of top US diplomat pledging to restore the department's "swagger," but his relative silence throughout the entire impeachment process -- particularly when it comes to defending career diplomats under attack -- has drawn anger and condemnation from the diplomatic community and caused morale within the department to plummet. And State's lack of transparency and cooperation throughout the matter has sparked suggestions of hypocrisy for the politician who built his career on the Benghazi hearings.

The new evidence was released to the public in tranches on Tuesday and Wednesday evenings.

The texts released Tuesday show Connecticut Republican congressional candidate Robert Hyde berating Yovanovitch and suggest he was monitoring her while she was in Kiev and relaying her movements to Parnas.

"F**k that bitch," Hyde wrote to Parnas in one message, writing the next day, "Wow. Can't believe Trumo (sic) hasn't fired this bitch. I'll get right in that."

In another, he relayed to Parnas, "Wake up Yankees man. She's talked to three people. Her phone is off. Computer is off. She's next to the embassy. Not in the embassy. Private security. Been there since Thursday."

"They are willing to help if we/you would like a price." he said in another message. Hyde told CNN Tuesday there was "no effing way" that he had been offering to harm Yovanovitch.

As these new developments were coming to light, Pompeo was in California for meetings with foreign counterparts and business leaders during a multi-day trip that was almost entirely closed to the press.

Diplomats alarmed

Amid the silence numerous former diplomats conveyed their alarm and horror at the idea a US ambassador was potentially being surveilled and threatened by another American. Retired US Ambassador Nancy McEldowney told CNN that Pompeo was "derelict in his duty for refusing to speak out about diplomats who are loyally and faithfully and professionally carrying out their responsibilities and who are being slandered by political attacks."

Yovanovitch, in a statement issued on her behalf on Tuesday by her lawyer, called the notion that her movements were being monitored "disturbing," adding that they trusted "that the appropriate authorities will conduct an investigation to determine what happened."

In its announcement about the investigation Thursday, Ukraine's Ministry of Internal Affairs suggested that the US should take part in the probe, noting "Ukraine expects the United States of America to respond to the appeal and looks forward to cooperation." The State Department has not said whether it intends to cooperate in the Ukrainian investigation.

Pompeo's comments Friday were the first public acknowledgment of the State Department's own inquiry into the matter. In a letter on Wednesday, Chairman of the House Foreign Affairs Committee Eliot Engel said that the head of diplomatic security had assured his staff on Tuesday night that they would "open an investigation into this matter immediately." However, a Senate Foreign Relations Committee aide told CNN on Thursday morning that they had not received the same guarantee.

The failure of Secretary of State Pompeo's department to answer key questions about its knowledge and response to these alleged threats as well as its noncooperation throughout the impeachment probe are a sharp departure from the priorities espoused by Pompeo when he served as a congressman from Kansas in the House of Representatives.

Pompeo pledged that the State Department would comply with the law during the House Democratic impeachment probe -- which he repeatedly denounced as "noise" -- but the administration attempted to stop witnesses from testifying and a senior State Department official ignored a subpoena to appear.

Pompeo accused Clinton of stonewalling over Benghazi

However, in 2015 during a House investigation related to the deaths of American personnel in the 2012 attack on the US consulate in Benghazi, Libya, Pompeo claimed in an interview with NPR that the committee had been "stonewalled by the State Department and by former Secretary (Hillary) Clinton."

And after Clinton's testimony to the committee in October 2015, the Kansas congressman emphasized the importance of the former secretary of state herself testifying.

"We had the Secretary of State under oath testifying, that is radically different than a State Department spokesperson standing at a podium responding to a media question. I think we owed it, frankly, to Secretary Clinton to give her an opportunity to explain from her point of view how decisions were made," he told C-SPAN at the time.

Pompeo's silence about Yovanovitch extends beyond this week's developments to as far back as the smear campaign against her led by Giuliani and his allies in March 2019. She was removed from her post in Kiev the next month.

However, texts turned over by House Democrats on Wednesday night show efforts by Giuliani and others to recall Yovanovitch in early February 2019 and suggest that Pompeo was apprised of these efforts by the President's personal lawyer in an earlier conversation than was previously known.

In a text exchange from February 10, 2019, between Victoria Toensing and Giuliani, the former wrote, "Is there absolute commitment for HER to be gone this week?"

"Yes not sure how absolute will get a reading in the morning and call you. Pompeii (sic) is now aware of it. Talked to him on Friday," Giuliani responded.

Emails turned over to American Oversight by the State Department in November showed that Pompeo spoke with Giuliani on March 26 and 29, 2019. There were no records provided that showed that Pompeo had talked to Giuliani in February.

The White House had to facilitate some of Giuliani's previously known interactions with Pompeo, according to documents and statements from the State Department and Giuliani himself. When Giuliani sent a packet of documents to Pompeo that were then turned over to the State Department inspector general, he said those materials were routed over through the White House. In a March 27, 2019 email included in the American Oversight tranche, Trump's former personal assistant Madeleine Westerhout reached out to the State Department on behalf of Giuliani's assistant to help arrange a call.

CNN reached out to the State Department on Giuliani's claim that he had spoken to Pompeo in early February. In numerous interviews during the impeachment inquiry, Pompeo dodged on questions about his knowledge and approval of Giuliani's role on Ukraine matters.

"I don't have much to say with respect to the Ukraine investigation," Pompeo said in November 2019.

This story was updated with comments from Pompeo on Friday morning.