Secretary of State Mike Pompeo has been accused of using his taxpayer-funded security detail to pick up his Chinese food, walk his dog, and bring his adult son from Union Station in Washington, DC, to the family's home, according to a State Department whistleblower.

Congressional investigators told CNN that Democrats "on a key House congressional committee" have begun probing the allegations against Pompeo.

Another issue raised by the whistleblower relates to Pompeo's wife, Susan.

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Secretary of State Mike Pompeo is under investigation by House Democrats following allegations that he used his taxpayer-funded security detail to pick up his takeout and walk his dog.

According to CNN, Democrats "on a key House congressional committee" are investigating the allegations, which were disclosed by a State Department whistleblower over a period of several months.

Pompeo isn't the first White House official to face scrutiny over taxpayer spending: former Interior Secretary Ryan Zinke spent nearly $139,000 to renovate three sets of office doors in need of repair; Housing and Urban Development Secretary Ben Carson doled out $31,000 for a mahogany dining set; and former Secretary of Health and Human Services Tom Price spent more than $1 million on travel (including $400,000 for private jets).

Read more: $1 million in private flights and a $31,000 table —here are the 6 Trump Cabinet members under scrutiny for their lavish spending of taxpayer money

While Pompeo didn't buy thousands of dollars' worth of furniture with taxpayer dollars, he is accused of instructing special agents to complete some questionable tasks while on the clock. For instance, CNN reported, citing the allegations by the whistleblower, that the secretary of state instructed a special agent to pick up Chinese food (without Pompeo in the car), retrieve his dog from the groomer, and pick up his adult son from Union Station in Washington, DC, and bring him to the family's home.

Agents said they felt like "Uber Eats with guns," multiple Democratic congressional aides told CNN, citing the whistleblower.

"Sending subordinates to run personal errands for you is the very definition of misuse of position," the former government ethics czar Walter Shaub told CNN. While Lon Fairchild, the special agent in charge of the Diplomatic Security Service, didn't dispute the allegations, he 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."

Another issue raised by the whistleblower relates to Pompeo's wife, Susan, who was assigned her own detail in 2018 despite being at home in the US. A former senior Diplomatic Security official told CNN that a full-time detail for a spouse was unusual.

There are also questions surrounding why Susan Pompeo has the privileges of a State Department staffer.

"[Secretary Pompeo] takes her on ... trips, has separate meetings, requiring control officers, motor pool assets, security, and time," a person familiar with the situation told CNN. "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."