The message was hidden for almost 65 years. A note in a bottle stuck behind concrete written by seven desperate inmates of the Nazi's Auschwitz concentration camp. The message in a bottle was discovered by workers renovating an old school building in the southern Polish town of Oswiecim, the site of the infamous Nazi German death camp.

"These were young people who tried to leave at least some sort of proof of their existence," said Jaroslav Mensfelt, historian with the Auschwitz-Birkenau museum.

Written in pencil on a rolled up piece of paper the note is dated September 9, 1944. It gives the names, camp numbers and hometown of the seven prisoners: Six from Poland and one from France. They all were aged between 18 and 20.

"We know that two of the Auschwitz prisoners who signed the message survived the camp, but their later fate is not known," Mensfeld said. "If they are alive, they would be in their eighties now. Perhaps the publicity surrounding this discovery will lead to more information."

The note was found as workers were taking down a wall in the school's basement. The building had belonged to the camp during Nazi occupation and had served as a warehouse for the camp's guards.

Nazi Germany established Auschwitz as part of the systematic genocide against European Jews during World War II. It's estimated that more than one million people – mostly European Jews – died in the Auschwitz-Birkenau camp alone. The victims also included Soviet prisoners of war, Romas and anti-Nazi resistance fighter from across Europe.