Buckingham Palace has denied reports that the Queen or Prince Philip have died.
When contacted by Newshub on Thursday afternoon (NZ time), a palace official said as far as he was aware, both Queen Elizabeth II and Prince Philip are "alive and well".
Speculation has been rife after one of the Queen's senior assistants reportedly called an "emergency meeting" at the palace.
According to the Daily Mail, staff from as far away as Scotland have been called in for the meeting in the early hours of Thursday morning (local time).
It was thought to be related to a major announcement concerning the Queen or Duke of Edinburgh.
Lord Chamberlain, the most senior officer of the royal household, and the Queen's Private Secretary Sir Christopher Geidt, are set to speak, the paper reports.
According to the Daily Beast, if Prince Philip were to pass in the middle of the night, a formal announcement would not be made by the palace until after 8am GMT (7pm NZT).
BBC's royal correspondent Peter Hunt confirmed a meeting has been called at Buckingham Palace, but said it's not believed to be about the health of either the Queen or Prince Philip.
The Queen is 91 and her husband turns 96 in June.
On Wednesday (local time), the Prince officially opened a new stand at the Lord's Cricket Ground. Images shared by the Royal Family Twitter account of the opening showed him appearing in good health.
Also on Wednesday, the Queen met with UK Prime Minister Theresa May, and there were no reports that Her Majesty was unwell after the meeting.