PHILADELPHIA (CNN) — The two German Shepherds belonging to President Joe Biden and first lady Jill Biden were returned to the Biden family home in Delaware last week after aggressive behavior at the White House involving Major Biden, two sources with knowledge tell CNN.

Major, who was adopted by Biden in November 2018 from a Delaware animal shelter, had what one of the people described as a “biting incident” with a member of White House security. The exact condition of the victim is unknown, however, the episode was serious enough that the dogs were subsequently moved to Wilmington, Delaware, where they remain.

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CNN reached out to the White House for comment and did not immediately receive a reply.

Major, who is 3 years old, is the younger of the two Biden dogs, and has been known to display agitated behavior on multiple occasions, including jumping, barking, and “charging” at staff and security, according to the people CNN spoke with about the dog’s demeanor at the White House. The older of Biden’s German Shepherds, Champ, is approximately 13 and has slowed down physically due to his advanced age.

Champ and Major moved into the White House in January, less than a week after Biden’s inauguration.

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“I’ve been getting obsessed with getting our dogs settled because we have an old dog and we have a very young dog,” Jill Biden told Kelly Clarkson last month during an appearance on “The Kelly Clarkson Show.” “They have to take the elevator, they’re not used to that, and they have to go out on the South Lawn with lots of people watching them. So that’s what I’ve been obsessed with, getting everybody settled and calm.”

Biden also said the only place the dogs are not allowed is on the furniture, though she admitted to catching Major on the couch. “They run all over,” said Biden.

A person familiar with the dogs’ schedule confirms to CNN they are in Delaware, but noted they have been known to stay there with minders when the first lady is out of town. Biden departed Monday afternoon for a two-day trip to Washington and California to visit military bases.

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