Letters that try to extort recipients for money have been sent to the homes of more than 2,000 teachers and other staff at elementary and junior high schools around the nation, it was learned Thursday.

The identical letters, whose sender is unknown, are all postmarked from the city of Tokushima and say the addressees have humiliated their pupils. They say the sender has been asked by the families of the victimized pupils to retaliate against the school officials, demanding a payment of ¥3 million.

The letters demand the money be sent to a woman who lives in Thailand, specifying an address there.