Anne Frank wrote one of the most poignant and memorable memoirs of the Holocaust. Now letters from her father Otto Frank have been discovered, revealing just how desperately he tried to save the family.

A file containing around 80 letters written by Anne Frank's father Otto Frank has been discovered in the archives of the New York-based YIVO Institute for Jewish Research, the Web site of Time magazine reported Thursday. The trove includes letters written by Otto Frank -- who survived the Holocaust -- between April 30, 1941 and Dec. 11, 1941, as well as letters from Frank's American relatives and a friend, Nathan Straus Jr., the son of the founder of Macy's department store.

The correspondence, which was discovered by volunteer archivist Estelle Guzik, details just how desperately the Franks tried to escape from the Netherlands, which was then occupied by the Nazis. The US consulate in the Netherlands had closed by the time of the letters, so Frank tried to find an escape route through Spain, with the aim of ultimately reaching neutral Portugal. He also tried to get visas to Paris and tried to arrange passage for the family to the US or Cuba.

YIVO has kept the existence of the letters quiet for the last year and a half while it explored legal and copyright issues. It announced Wednesday that it would release the documents at a press conference on Feb. 14.

The question remains as to why Frank's pleas were not answered. According to YIVO executive director Carl Rheins, the file raises uncomfortable questions about US immigration policy at the time.

The Franks were a German Jewish family who moved to Amsterdam from Frankfurt after the Nazis came to power. They took refuge in a neighbor's attic in July 1942 and hid there for over two years before being arrested. Anne Frank described the family's time in hiding in a diary that has become one of the world's most widely read books.

Anne Frank died of typhus in the Nazi concentration camp Bergen-Belsen, Germany in 1945. She was 15 years old. Her father survived the war and later returned to the Netherlands to collect his daughter's notes. They were published in the Netherlands in 1947, with an English-language version being published in 1952.