Prince Philip, Queen Elizabeth II's 91-year-old husband, was hospitalized in London on Thursday, June 6, for an "exploratory operation," a Buckingham Palace rep told Us Weekly. He was admitted to London Clinic shortly after one of the Queen's summer garden parties, following earlier "abdominal investigations."

"The Duke of Edinburgh is expected to stay in the hospital for up to two weeks," the rep added. "Further updates will be issued when appropriate."

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A source tells Us that "routine tests" by palace doctors led to the so-called "abdominal investigations," which then led to the Prince's "planned admittance" to the hospital. News of his pending operation comes just a few days after the Prince canceled an official engagement because he was "just a bit under the weather"; however, the surgery is not thought to be related to that illness. It's also not thought to be related to his recent bladder problems or blocked coronary artery.

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"He is not in pain and in good spirits," the source tells Us, adding that the operation is scheduled to take place on Friday, June 7. "The Queen is being kept fully informed. Understandingly, she's concerned."

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Philip, who will turn 92 on June 10, is expected to miss at least two events in the next couple of weeks, including Trooping the Colour on Saturday, June 15. He was last hospitalized in August 2012 with a bladder infection.

This article originally appeared on Prince Philip Hospitalized for "Exploratory Operation," Is in "Good Spirits"