"We hope the main works will be completed before the end of the year," said Agnieszka Kowalczyk-Nowak of the project, which is being funded by Poland, Slovakia, Hungary and the Netherlands.
The Sobibor death camp during World War II was the site of crimes of Ukrainian-born John Demjanjuk who was convicted in 2011 in Germany as an accessory to the murder of almost 30,000 Jews while acting as a guard at the camp.
After an uprising at the Sobibor camp in October 1943, the Nazis razed it and built a farm there in an attempt to conceal any trace of their crimes, which included the deaths of around 2,50,000 Jews over the previous two years.
During the prisoners' revolt, around 300 inmates managed to flee but most were later rounded up in the nearby forests and executed by Hitler's feared SS secret police.
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The new museum is expected to be opened to the public in 2019, according to Kowalczyk-Nowak.
A first, smaller museum at the former Nazi German death camp was shut down in 2011 due to underfunding.
The Nazis set up a string of death camps in occupied Poland where they brought Jews deported from throughout Europe.
The most notorious of these was the Auschwitz-Birkenau camp, which has become emblematic of the Nazi Holocaust. It was there that 1.1 million people, most of them Jews, were killed from 1940 to the start of 1945.