Pope Francis died from a cerebral stroke that led to a coma and irreversible heart failure, the Vatican has said.
A death certificate released for the 88-year-old pontiff said he had fallen into a coma before his death, which was announced on Monday.
The Vatican released the Pope's final testament, in which he outlined his request to be buried "in the ground, without particular ornamentation" but with the inscription "Franciscus".
Francis said he wished to be buried in Rome's Basilica of Saint Mary Major, rather than at St Peter's Basilica in the Vatican, where many previous pontiffs have been laid to rest.
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His coffin might be moved to St Peter's Basilica as early as Wednesday morning to allow the faithful to pay their respects, a Vatican spokesman said.
The Pope had suffered from a chronic lung disease and had part of a lung removed as a young man.
Health issues plagued him throughout his later life, and he was admitted to Gemelli hospital in Rome on 14 February for a respiratory crisis that developed into double pneumonia.
This led to a 38-day stay in hospital, the longest of his 12-year papacy.
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But the leader of the world's Roman Catholics emerged on Easter Sunday, a day before his death, to bless thousands in St Peter's Square.
Before the public appearance, the Pope "exchanged good wishes" with US vice president JD Vance during a private audience at the Vatican.
Bells tolled in church towers across Rome after the announcement of his death.
Francis, the first Latin American pontiff, charmed the world with his humble style and concern for the poor, but alienated conservatives with critiques of capitalism and climate change.
Seven days of mourning will be observed in his native Argentina, as well as in its heavily-Catholic neighbour, Brazil.
While no date has yet been set for the funeral, the Vatican said it would normally be expected to take place sometime between Friday and Sunday.
Cardinals are due to meet on Tuesday and could set the timetable for the funeral then.
news.sky.com