Polish authorities have reopened an investigation into crimes committed at Auschwitz and its satellite camps during World War II.It is estimated that one million people - mostly Jews and non-Jewish Poles - were killed at the Nazi death camp.One aim is to track down any Nazi war criminals still living.It is being carried out by the Institute of National Remembrance, a state body that investigates Nazi and communist-era crimes.The new investigation was opened by the institute\'s branch at Krakow, which is near Auschwitz.It was not immediately clear if investigations into other death camps operated across German-occupied Poland - such as Treblinka, Sobibor, Chelmno and Belzec - were also planned.Poland originally launched investigations in the 1960s and 1970s into crimes at Auschwitz, but closed them in the 1980s without any indictments being made.During the communist era, Poland had difficulty questioning witnesses and perpetrators living abroad because the country was part of the Soviet bloc.\"We do not discount the possibility of finding alive former employees of the Auschwitz-Birkenau concentration camp, in which case they may be accused of crimes against the Polish nation,\" said Piotr Piatek, of the Remembrance Institute in Krakow.Most camp employees were tried in Poland after World War II, accused of crimes against the country, although these trials were ended by an amnesty in 1956.The last time Poland prosecuted anyone for Nazi crimes was in 2001, when a Pole, Henryk Mania, was sentenced to eight years in prison for taking parts in acts of genocide in Chelmno.Leading international Nazi hunter Efraim Zuroff praised Poland\'s reopening of the investigation.He said it \"could have tremendous implications\" in paving the way for new prosecutions, thanks to the precedent set by the conviction earlier this year of Ohio car worker John Demjanjuk, after his extradition from the US for trial in Germany.Demjanjuk was convicted of 28,060 counts of accessory to murder during the time he was a guard at the Sobibor extermination camp in Poland.