Newly discovered letters written by Otto Frank chronicle a father's desperate efforts to get his family out of the Netherlands.

Anne Frank's father wrote to relatives, friends and officials and investigated escape routes through Paris and Spain in an effort to save his family from the Nazis, who occupied the Netherlands in 1940.

Anne Frank, right, and her father, Otto Frank, are seen at Amsterdam Town Hall in July 1941. Other people in the photo are unidentified.
(Anne Frank Foundation/Associated Press)

In 1942, Frank, his wife and two daughters and another family went into hiding in a warehouse in Amsterdam. They were discovered by the Nazis more than two years later.

The Diary of Anne Frank, a description of their life in hiding written by his youngest daughter and published after the war, has sold 25 million copies, and their hiding place is now a museum.

The YIVO Institute for Jewish Research, a New York-based institution that focuses on the history and culture of Eastern European Jews, said it discovered Frank's letters among 100,000 other Holocaust-related documents.

"We have come across the file which belonged to Otto Frank, documenting his efforts to emigrate his family and get them out of Holland," Cathy Callegari, a spokeswoman for YIVO, said on Thursday.

The institute said it found the letters 18 months ago, but did not reveal them until now because it had to explore legal issues.

On Feb. 14, it plans to release Frank's letters, documents and records from various agencies that helped people emigrate from Europe.

Frank was attempting to get his family out of the country to the safety of Cuba or the United States.

Some of the letters to relatives and officials were written between April 30, 1941, and Dec. 11, 1941, when Germany declared war on the United States.

He also made attempts to get visas so they could travel via Paris and to investigate escape through Spain to Portugal, but was unsuccessful.

The letters are of particular interest to the Anne Frank Foundation in Basel, Switzerland, which holds the rights to her writings, said Bernd (Buddy) Elias, Anne Frank's cousin and the president of the foundation.

"We would love to have them in our archive. I mean, we are the heirs of Otto Frank," Elias said.