(CNN) Two Secret Service agents are facing an internal investigation over their alleged conduct last week while they protected a grandchild of President Donald Trump, people familiar with the matter tell CNN.

The actions of the two agents, who are assigned to the protective detail for the children of Donald Trump Jr., are being reviewed by the internal affairs division of the Secret Service. The questions involve photographs the agents may have been taken of one of the children while being driven around New York on Sunday.

The agents allegedly took a picture of a child sleeping in the Secret Service vehicle, according to people familiar with the matter. Neither of the boy's parents, Donald Trump Jr. and his wife, Vanessa, were present at the time, but after learning about it, they voiced concern and raised questions with the agents' supervisors.

The two agents were questioned on Monday, CNN has learned, and the matter is being reviewed internally by the Secret Service.

Catherine Milhoan, a spokeswoman for the Secret Service, cautioned against drawing any "conclusions that may grossly mischaracterize the matter."

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