UPDATE II: The Vatican released the following statement Wednesday evening: "This afternoon, Mrs. Cristina Fernández de Kirchner, President of the Republic of Argentina, telephoned the Holy Father to offer him condolences on behalf of the Argentine people for the bereavement that has affected his family." 
 

UPDATE I: At his weekly general audience on Wednesday, the Holy Father said:

"I thank you for the prayers and condolences for what happened in my family. Even the Pope has a family. We are 5 siblings, I have 16 nieces and nephews. One of these nephews had a car accident. His wife died as well as two young children; one was 2 years old and the other only a few months old. And he right now is in critical condition. I thank you so much, so much, for your condolences and prayers."

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Pope Francis is "deeply saddened" on hearing the news that three of his relatives have died in a car accident in Argentina, according to Vatican spokesman Father Federico Lombardi. 

The Pope's grandnephews, Antonio aged 8 months and Jose aged two, were killed along with their mother, 39-year-old Valeria Carmona. The Holy Father's nephew, Emanuel Horacio Bergoglio, is in hospital in critical condition, according to AFP.

Their car was travelling between Cordoba and Rosario when it struck a truck loaded with corn, reports say. 

Emanuel Horacio, 35, is the son of the Pope's late brother, Alberto Bergoglio.

Father Lombardi said the Pope "was informed of the tragic accident in Argentina involving some of his family and is deeply saddened." He added the Pope "calls on all those who share in his grief to join him in prayer."