LONDON - The intruder who was arrested on Christmas morning on the grounds of Windsor Castle, where Queen Elizabeth II is living, was carrying a crossbow, police said on Sunday. The man has been detained under the Mental Health Act, they said. 

Officers arrested the 19-year-old Southampton man shortly after he entered the castle grounds around 8.30 a.m. Saturday, police said. He did not enter any any buildings on the estate.

The queen was home at the time.

The man was "arrested on suspicion of breach or trespass of a protected site and possession of an offensive weapon," Thames Valley Police said in a statement on Saturday. They said that security processes were triggered "within moments" of the intruder entering the grounds.

In a follow-up statement on Sunday, the London Metropolitan Police said that "following a search of the man, a crossbow was recovered." The force added that the man had undergone a mental health assessment and has been "sectioned under the Mental Health Act and remains in the care of medical professionals."

Several British tabloids, citing unnamed sources, reported Saturday that the intruder had a crossbow and had used a rope ladder to scale a fence.

"Queen's Xmas Crossbow Horror," read a front page headline in Sunday Mirror.

A spokeswoman for Buckingham Palace declined to comment, saying it was a matter for the police.

The incident was only the latest security breach at Windsor this year. In May, a couple was arrested after entering the grounds of the Windsor estate. The Times of London reported that they were found near the spot where the queen walks her dogs.

One of the best known royal security breaches over the years occurred in 1982, when 31-year-old Michael Fagan broke into Buckingham Palace. He reached the queen's bedroom and spent several minutes chatting with the monarch. The incident was later depicted in an episode of "The Crown."

The queen had been planning to host a Christmas gathering this year at her Sandringham estate in Norfolk, England. But those plans were scrapped, for the second year in a row, after a surge in coronavirus infections. Confirmed daily cases hit a record high on Saturday.

Instead, the queen spent Christmas Day at Windsor Castle, her main residence since the start of the pandemic in 2020. She was joined by a small group of family members, including her eldest son, Prince Charles, and his wife, Camilla.

It was the queen's first Christmas since the death of her husband, Prince Philip, in April at age 99. The queen paid tribute to him in her annual Christmas Day speech, which was broadcast Saturday but recorded last week.

Referring to Philip, the queen said that there was "one familiar laugh missing this year."