NHK has learned that Japanese students sent letters to the United States to express appreciation for relief aid after the Great Kanto Earthquake, which hit Tokyo and surrounding areas on September 1, exactly 100 years ago.

Japan received relief assistance after the massive quake from countries around the world, including the US.

A research team at Tohoku University in northeastern Japan says it found a total of 744 letters written in English by Japanese students.

They say the letters were kept by descendants of US President Calvin Coolidge, who was in office from 1923 to 1929.

They also say a group named The Japan Students Association called on universities and other schools across the country to write the letters, and sent them to the US government in May 1924.

In the letters, the students express gratitude for the US aid and say they will pass their thanks on to their descendants. They also say their towns were destroyed by the quake but that they are determined to restore them.

Japan at the time had chilly relations with the United States, where there was a movement to expel Japanese immigrants. But the US provided Japan with generous assistance, including goods and cash donations.

The research team says the students may have been trying to improve relations between the two countries by sending the friendly messages.

Team leader Ono Yuichi of Tohoku University's International Research Institute of Disaster Science says the letters show that bonds between people, irrespective of social situations or international relations, are important for building peace.