Mother Teresa of Calcutta, the Nobel laureate known for dedicating her life to helping the poorest of the poor, will be made a saint of the Roman Catholic Church, the Vatican said on Friday.

Pope Francis has cleared the way for sainthood by approving a decree recognizing a second miracle attributed to her intercession with God – a necessary event for such a move in the church.

Mother Teresa, who died in 1997 at the age of 87, become an international icon of charity in the 20th century but has also been criticized for trying to convert people to Christianity. She was beatified in 2003 by the late Pope John Paul II. Beatification, which requires one miracle, is the last step before sainthood, which requires two.

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The church believes saints are holy men and women who lived extraordinary lives of virtue and are believed to be in Heaven with God.

Francis, who has made concern for the poor a major plank of his papacy, was keen to make Mother Teresa a saint during the Church's current Holy Year, or Jubilee, in which Catholics are called on to emphasize the need for mercy and compassion in the world.

Mother Teresa's second miracle involved the inexplicable healing of a Brazilian man who was suffering from a viral brain infection that resulted in multiple abscesses with hydrocephalus, according to Church officials.

Relatives prayed to Mother Teresa and he recovered, leaving his doctors at a loss to explain how. A Vatican medical commission deemed the sudden recovery "inexplicable in the light of present-day medical knowledge," according to Father Brian Kolodiejchuk, the chief promoter of the sainthood cause.

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In Calcutta, Sunita Kumar, spokeswoman for Mother Teresa's Missionaries of Charity religious order said the nuns were "over the moon" when they got the news.

"We thought her whole life was a miracle. Her whole life was dedicated to the poor and there was nothing else in her mind than service. Everyone was accepted and there was no obstruction in her work," Kumar said. 

Known as the "saint of the gutters", the diminutive nun is expected to be canonized – formally made a saint – in early September. It was not clear if the ceremony would take place in Rome or if the pope would travel to India to preside over it.