Washington (CNN) Former US Ambassador to Ukraine Marie Yovanovitch on Tuesday called for an investigation into the "disturbing" notion that she was under surveillance from associates of the President's personal lawyer, Rudy Giuliani.

With the release of texts turned over to House investigators by indicted Giuliani associate Lev Parnas, Yovanovitch has once again been ensnared at the heart of the still-widening scandal that has already resulted in the impeachment of President Donald Trump. And once again, the diplomatic community is rallying to support her -- expressing outrage over her treatment.

The texts released by the House Democrats 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. Hyde declined to comment to CNN when asked if he had surveilled Yovanovitch, who served as a key witness in the House impeachment probe.

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

A spokesperson for the Southern District of New York -- where Parnas is indicted -- declined to comment. The State Department did not immediately reply to requests for comment about a potential investigation and the texts.

Although the people who spoke with CNN noted that surveillance is a common problem for diplomats abroad, they expressed shock and horror Tuesday at the idea that the longtime diplomat was being surveilled by an American.

"It's horrifying, it's just unbelievable," retired ambassador Jim Melville said in a phone conversation with CNN. "The very idea that there were elements, possibly of the US government or connected to the US government, who were trying to do an end run around everything that we've established to keep our mission safe is just outrageous."

Retired ambassador Nancy McEldowney echoed that sentiment.

"I find this really shocking and alarming and the idea that American citizens would be surveilling an American ambassador with the endorsement of the President's personal attorney, it's just so troubling to me," McEldowney told CNN.

Another retired ambassador said they had "never heard of anything like it."

"It's common that terrorists and former communists do this to us. It's appalling and incomprehensible that somebody who is working for the President's personal lawyer would have been doing this to our ambassador," they told CNN.

That ambassador explained that surveillance is a "real problem" that's "unfortunately pretty common" for diplomats. Embassies have "surveillance detection teams" -- normally locally hired staff -- "who actually are out there looking to see if anyone is showing unwarranted interest" in embassy operations, they said.

"There are lots of different possible motives" for surveilling diplomats, the official said, explaining that it is normally used for terrorism or intelligence gathering -- sometimes to find embarrassing information on a person.

That official said Yovanovitch may have known she was being surveilled, noting that in a country like Ukraine that would not be unusual.

However, Melville said her awareness could have been dependent on "how attentive the host security services -- the Ukrainians in this case -- and our own law enforcement personnel and our diplomatic security personnel were being. It wouldn't be something that she would be expected to notice."

"It would be something that you would trust that the mission and the structure would be aware of and keep her safe from," he said. "When you're looking for threats, you're looking in certain directions. You're not necessarily checking behind on your own people, and you have to trust that they have your back, not that they're working behind your back."

Embassy personnel assume they are monitored

Three sources familiar with the matter told CNN that personnel at the embassy always assume they are being monitored, including through conversations on their cell phones. They were aware that local Ukraine security was always tracking them, the sources said, and did not discount the possibility that someone from a local cell phone company could be paid off to track a certain cell phone, although the sources did not have evidence of that.

It is not hard to know where the US ambassador is, the sources said, as they have high visibility in Kiev and someone can easily be tipped off to keep an eye on the ambassador's movement around the embassy. Sources say there are apartment buildings close to the facility where someone could easily have eyes on the embassy and staff are keenly aware that the office is visible in broad daylight from the outside.

The sources familiar told CNN that Ambassador Bill Taylor -- who took over as charge d'affaires after Yovanovitch's removal -- and other diplomats who recently worked at the US Embassy in Kiev had never met or heard of Hyde until the documents were released Tuesday night.

Yovanovitch, who was recalled from her post in Kiev in May 2019 after a smear campaign led by Trump's allies, has been repeatedly maligned by the US President. He told his Ukrainian counterpart in July 2019 that she was "going to go through some things," according to a rough White House transcript of the presidents' conversation -- a message Yovanovitch said she found threatening.

In her public testimony in November 2019, Yovanovitch called on State Department leadership to do more in the face of the attacks on her and her fellow foreign service officers.

Asked whether they believed it would be helpful for Secretary of State Mike Pompeo to come out in Yovanovitch's defense in light of the latest developments, both Melville and McEldowney slammed the top US diplomat.

"He hasn't stood up for anybody in the foreign service. All he's looking out for is his own back and the President," Melville said. "He has no interest in the good of the service and its people and he's made that abundantly clear repeatedly."

McEldowney told CNN she believes Pompeo is "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."

The State Department did not reply to a request for comment about the criticism.