SOURCE: ABC.NET.AU

Gabriel García Márquez left over 100 letters in a box marked with the word, "grandchildren".(AP: Fernando Llano)

While reviewing the photo archives left by Nobel Prize-winning Colombian author Gabriel García Márquez, one of his granddaughters came across a mysterious plastic box with the word "grandchildren" written on its label. 

At first, Emilia García Elizondo was afraid to open the box but curiosity overcame her.

Inside were 150 unpublished letters that he received from Chilean poet Pablo Neruda, former US President Bill Clinton, Cuban President Fidel Castro and actor Robert Redford, among others.

Forty of the letters will be exhibited for two months starting on June 16 in the colonial house in the southern part of Mexico's capital where Mr García Márquez lived with his wife, Mercedes Barcha, from the 1980s until his death in 2014.

The exhibition is part of celebrations for the 40th anniversary of his winning the Nobel literature prize.

From one literary great to another, Pablo Neruda also penned a letter to Gabriel García Márquez.(AP: Fernando Llano)

Another event, which includes the exhibition "Gabriel García Márquez: The Making of a Global Writer," will open on June 18 in Mexico's Museum of Modern Art.

"I'm 32 years old and all this continues to impress me," Ms García Elizondo, who is director of the García Márquez foundation, told The Associated Press, describing her shock at finding the box in a cabinet on the second floor of her grandparents' house.

She had passed the cabinet many times without paying much attention to it.

Mr García Márquez's granddaughter said the discovery was a surprise for the family because they thought all his letters and personal correspondences were in the Harry Ransom Center at the University of Texas at Austin, which possesses the largest collection of the writer's documents.

US film director Woody Allen wrote that he was "still scared of coming to Colombia — my wife doesn't like to pay ransom".(AP: Fernando Llano)

"One never expects to find this kind of thing even though one already knows who Gabo is. I will always think that Gabo does everything like magic," she said.

Mr García Márquez is know affectionately in Latin America as Gabo.

Among the letters that will be exhibited are five from Castro, one from Neruda, two from Mexican writer Carlos Fuentes, two from Mexican guerrilla leader Subcomandante Marcos, one from Mr Redford, one from director Woody Allen and seven from Mr Clinton.

In one of them, dated December 28, 1999, Mr Clinton told the Colombian writer the emotion he and his wife, Hillary, felt at a concert of Colombian vallenato music given by young people at the White House.

Bill Clinton typed his letter, in which he wishes "Gabo" well during the Holy season, signing it "Bill" by hand.(AP: Fernando Llano)

He described the music as a "treasure" and a "wonderful counterpoint to the negative images often associated with your beautiful country."

Also included is a letter that Mr Castro wrote by hand, dated December 10, 2007, in which he writes: "I am subject to a rigorous exercise regimen that I must not fail to comply with if I intend to continue being useful to the revolution."

Gonzalo García Barcha, the writer's youngest son and Emilia's father, said the family misses Mr García Márquez very much.

Mr García Márquez has four grandchildren.

"That's why we do these kinds of activities. We want to keep this house alive," he said.

AP