The letters and photos of a young Oskar Schindler have been discovered by a relative who had no idea that "Uncle Oskar" had saved the lives of more than 1,000 Jews.

The correspondence was found by the daughter of Schindler's cousin, Emilie Tyrolt, who emigrated to America before 1920 and exchanged letters with the young Oskar.

A letter, a postcard and two photographs went to auction yesterday at New York's Kestenbaum & Company, and were expected to fetch around £4,000.

The auction company's director, Daniel Kestenbaum, said Emilie Tyrolt's daughter wants to keep her identity secret.

Mr Kestenbaum said: "She is now in her 80s and was on a tour of Israel with her Wisconsin church group four years ago and was told about Schindler by her tour guide - a Holocaust survivor.

In her attic, she found a letter from 12-year-old Schindler

"Intrigued, she spoke to the tour guide and asked if Schindler was someone well-known. The guide was taken aback and told her the story, and she said: 'Oh my, that was my mother's cousin.' She was taken on an official visit to Mount Zion to visit his grave."

Returning home, she searched her attic and found a letter from 12-year-old Oskar and his mother, Fanni.

The letter, written in German, gives little indication of what the boy would go on to achieve. Schindler writes about his schooldays and asks for stamps for his collection. His mother writes about the depression in post-war Germany and hyperinflation.

Fanni writes: "I am now afraid of travelling… formerly it was a pleasure, but the war has ruined everything." She also mentions that her son has grown "uncommonly tall".

Also discovered was a postcard, believed to have been written by Schindler, and two photographs, one of him in military costume aged eight.

Very little has been discovered about Schindler's early life. In 2004, Professor David Crow published his definitive biography, Oskar Schindler, The Untold Account of his Life, in which he notes on the third page that practically nothing is known about Schindler's childhood.

Schindler, a German industrialist and Nazi party member, saved more than 1,000 Jews from the Holocaust. He protected Jewish forced labourers working in his factories after he saw many murdered in the Krakow ghetto.

He spent his entire fortune on bribes to protect his workers from the SS and was left destitute.

His story is told in the Oscar-winning Steven Spielberg film, Schindler's List.