The cause of Queen Elizabeth II's death remains a mystery, but the public will soon know about it after the period of mourning next week. The news about Her Majesty's demise came on Thursday, September 8, at the age of 96.

For a while, there were talks about Queen Elizabeth's deteriorating health. However, there were very few details as to what caused her passing.

Express noted that all inquiries in Aberdeenshire were forwarded to the National Records of Scotland (NRS). Last week, the state agency revealed it would remain mum about the questions regarding the cause of her death until the period of mourning ended.

The period of national mourning will end on Tuesday, September 27, while the royal mourning will continue until 8 a.m. on the said day.

In Scotland, the registration of deaths is required, following the Registration of Births, Deaths and Marriages (Scotland) Act of 1965. The act notes that every death happening in the country should be registered.

It includes submitting the death certificate to the registrar, which must be done within seven days after death. If Queen Elizabeth died in England, releasing an official cause of death would not be required, considering the Registration Act of 1836 doesn't cover the monarchs.

However, in Scotland, doctors must report all deaths, whether "sudden, suspicious, accidental or unexplained" to the Crown Office. The Crown Office in Edinburgh said her death "hadn't been referred to it" because it "wasn't a death that required to be," per Scottish Daily Express.

Meanwhile, before Queen Elizabeth passed, all her children, King Charles III, Princess Anne, Prince Andrew, and Prince Edward, rushed to her side in Balmoral. At the time, her doctors revealed they were "concerned" about her health and recommended that she remain "under medical supervision," per The DailyMail.

A few hours after the announcement, she died surrounded by her family. Her death was confirmed at 6:30 p.m.

Later, a Buckingham Palace spokesman revealed the queen died peacefully. After her death, Britain and other Commonwealth realms would enter ten days of mourning.

Her coffin was moved to London on the royal train through Edinburgh before lying in state in Westminster Hall in the Houses of Parliament for four days. The state funeral took place at Westminster Abbey in central London on Monday, September 19, attended by her family and 2,000 heads of state, prime ministers, presidents, European royals, and key figures from around the world.