Letters from Anne Frank and her sister to pen pals in Iowa, written before the Nazi invasion of the Netherlands, have surfaced and are due to be sold at an auction, The New York Times reported Friday.

The two letters, a postcard and two passport-size photographs of the Jewish sisters are dated April 27 and April 29, 1940, a month before the Nazis invaded the Netherlands and before the girls were forced to hide in a Dutch house in an attempt to escape their persecutors.All the items are to be auctioned by Swann Galleries in Manhattan on Oct. 25, the paper said.

The letters to two sisters in Danville, Iowa, were written in English and expressed little of the world about to explode about them.

"I am sitting in the fifth class," the 11-year-old Anne Frank wrote. "We have no hour-classes we may do what we may prefer, of course we must get to a certain goal. Your mother will certainly know this system, it is called Montessori."

Anne's older sister Margot, then 14, discussed the threatening political situation, but with little alarm.

The letters were sent to Betty Ann Wagner and her sister, Juanita, of Danville, Iowa, who were the same age as the Frank girls.

Living on a farm in Danville, Iowa, the Wagners started the correspondence at the suggestion of a teacher. The Wagners said they learned of the girls' deaths in concentration camps from their father who wrote to them.

"I just sat and cried," Betty Wagner said in an interview with the Times. "To be very honest, we grew up in a small country town; it never dawned on me that the other girls were Jewish. If we had known, we would have prayed and done more. But it never occurred to us, until we heard from Mr. Frank."

Wagner said she decided to sell the letters under the advisement of a good friend who is also a financial adviser.