Washington (CNN) Democrats on a key House congressional committee are investigating allegations from a whistleblower within the State Department about Secretary of State Mike Pompeo and his family's use of taxpayer-funded Diplomatic Security -- prompting agents to lament they are at times viewed as "UberEats with guns".

Congressional investigators, who asked for the committee not to be named as they carry out their inquiries, tell CNN that a State Department whistleblower has raised multiple issues over a period of months, about special agents being asked to carry out some questionable tasks for the Pompeo family.

In April, for example, an agent was asked to pick up Chinese food—without Pompeo in the car. The whistleblower said this led agents to complain that they are now serving as "UberEats with guns," which has created a buzz within the department, according to multiple Democratic congressional aides who cited the whistleblower.

On another occasion, the whistleblower told aides, a Diplomatic Security special agent was given the job of picking up the Pompeo family dog from a groomer.

And CNN has seen a document given to the committee aides by the whistleblower showing that in January, Diplomatic Security was asked by a person in Pompeo's office to pick up his adult son from Union Station in Washington and bring him to the family home.

Lon Fairchild, the special agent in Charge of the Diplomatic Security Service, did not deny that the specific trips, such as the dog or the takeout food, were carried out by agents, but said in a statement, "I was head of Secretary Pompeo's security detail since his first day on the job. At no point during my service did he or any member of his family ask me or any member of my team to act in any way that would be inconsistent with our professional obligation to protect the Secretary 24-hours a day, 7-days a week."

A former senior Diplomatic Security official told CNN such tasks would not be appropriate—especially without the Secretary himself in the car at the time—unless some specific threat was identified that necessitated those trips. For example, they said when former Secretary of State Warren Christopher started in the job, he had hoped his agents would go get groceries for him, but had to be told that that's not what they do.

The Diplomatic Security Service is the law enforcement and security arm of the State Department tasked with protecting US diplomacy and diplomats worldwide and securing the integrity of US travel documents.

While protecting the security of the secretary of state is an important task for the service, there are concerns that agents may have been asked to carry out inappropriate tasks while assigned to Pompeo.

According to the Code of Federal Regulations, a federal employee "shall not encourage, direct, coerce, or request a subordinate to use official time to perform activities other than those required in the performance of official duties or authorized in accordance with law or regulation."

It is unclear if Pompeo requested the allegedly improper arrangements or whether they were made by someone on his staff without his knowledge.

But the whistleblower said there is a culture within Diplomatic Security to try and please the secretary and avoid upsetting him.

Former government ethics czar Walter Shaub told CNN "sending subordinates to run personal errands for you is the very definition of misuse of position."

Concerns about Susan Pompeo's security arrangements

Those personal-seeming tasks might be eye-catching, but congressional investigators say the State Department whistleblower told them the bigger issue causing concern among some agents is the question of why Pompeo's wife, Susan, has her own security detail, assigned to her in 2018, even while she is at home in the United States.

"There is a lot of confusion among agents over this, over why this is justified," one aide told CNN. "Because according to this source they have seen nothing to indicate it is justified. In fact just the opposite. It's their understanding there was no finding of a high-enough level threat to merit this detail." The whistleblower told these investigators that multiple special agents and supervisors within Diplomatic Security understood that a formal threat assessment had not been carried out, under longtime standard operating procedure, and that there is no specific threat against Susan Pompeo

Furthermore, the whistleblower told aides that shortly after Susan Pompeo received her personal security detail, in July 2018, agents were verbally told not to use her callsign—which is "Shocker"—over the radios or publicly. The reason, according to one aide, citing the whistleblower, was that "they knew it wasn't kosher."

CNN has viewed an email from within the State Department confirming that she has an agent assigned to her, along with her callsign. The assistant secretary overseeing Diplomatic Security, Michael Evanoff, was included in the correspondence. The subject line says "Shocker Detail."

The former senior Diplomatic Security official who asked not to be identified said that such a full-time detail for a spouse is unusual and would only be assigned once a formal process was followed, assessing the need for such security. They said that the risk investigation would be performed by Diplomatic Security's Protective Intelligence and Investigations Division, in the Office of Threat and Intelligence Analysis. The former official told CNN this protocol has existed within Diplomatic Security for decades. And that in this person's lengthy tenure at Diplomatic Security, no spouse was ever given a security detail for more than a short, specific period of time.

One congressional aide told CNN that under the current administration, "We have a lot of concerns over how things are being conducted within Diplomatic Security. There is a lack of transparency."

A State Department spokesperson insisted that a threat assessment for Susan Pompeo was carried out by the Protective Intelligence and Investigations Division, but would not tell CNN when that happened.

"The provision of a protective detail to Mrs. Pompeo is expressly authorized by federal law. In this case, Diplomatic Security determined that the threat warranted the provision of such a protective detail to Mrs. Pompeo and began providing it as of July 28, 2018."

In a statement, Assistant Secretary of State for Diplomatic Security Michael Evanoff said, "The Diplomatic Security Service has been protecting the spouse of the Secretary of State since the 1970s as the security threat dictates. We are a federal law enforcement agency, and this is an integral part of our core mission. Today the security threats against Secretary Pompeo and his family are unfortunately very real. The Diplomatic Security Service is proud to protect the Pompeo family from those who would harm the Secretary of State and the United States."

Concerns about how Trump admin officials have used government resources

These questions about Pompeo are the latest in a slew of ethics allegations surrounding Trump administration Cabinet secretaries and their use of government resources.

Former Environmental Protection Agency administrator Scott Pruitt left his position after a series of ethical questions about his security team; the former head of Health and Human Services, Tom Price , resigned after a scandal over his use of private planes; Housing and Urban Development Secretary Ben Carson was assailed for extravagant taxpayer-funded furniture purchases . Interior Secretary Ryan Zinke stepped down amid probes of his real estate dealings and conduct in office. And Former Secretary of Veterans Affairs David Shulkin left that job under an ethics cloud after a damning inspector general report criticized him for improperly accepting gifts and misrepresenting travel plans.

The aides said another whistleblower has come forward, who worked on the State Department's executive seventh floor where the secretary of state and top aides are based—telling them that employees there have been told not to put information concerning Susan Pompeo into official emails, so that it would not be preserved in required recordkeeping.

The role Susan Pompeo has played within the State Department and when the secretary travels is another area of concern to congressional aides, Diplomatic Security officers and multiple sources within the State Department and the CIA, which Pompeo previously led.

Several sources told CNN when Susan Pompeo accompanies the secretary on certain trips she has not only had a dedicated special agent to tend to her, but also a State Department staffer.

They said that ahead of a recent trip to Kansas, during which she accompanied her husband, she had at times chaired meetings on trip logistics at the State Department, which raised eyebrows, including of senior State officials.

One person familiar with the situation called it "the worst kept secret at State," telling CNN, "[Secretary Pompeo] takes her on ... trips, has separate meetings, requiring control officers, motor pool assets, security, and time. It was especially brazen during the shutdown when people were actually called into the embassy while furloughed. Just one more thing killing morale at the department."