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They also discovered human  remains as they dug into the ground, and on the surface "large  quantities of ashes mixed with sand, among which are numerous human  bones".Despite this, in a later statement they said they had discovered no mass graves.The existence of mass graves was known about from witness  testimony, but the failure to provide persuasive physical evidence led  some to question whether it could really be true that hundreds of  thousands of Jews were killed here.Although they lasted only a few days, those post-war  investigations remained the most complete studies of the camp until I  began my work at Treblinka in 2010.This revealed the existence of a number of pits across the site."Start Quote
Bone fragments can still be seen on the surface of the ground, especially after rain"
Mapping the Treblinka death camp Continue reading the main story
About 800,000 Jews - almost one in six victims of the Holocaust - were slaughtered at Treblinka between spring 1942 and August 1943
Some may be the result of post-war  looting, prompted by myths of buried Jewish gold, but several larger  pits were recorded in areas suggested by witnesses as the locations of  mass graves and cremation sites.
One is 26m long, 17m wide and at least four metres deep, with a ramp at the west end and a vertical edge to the east. 
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Another five pits of varying  sizes and also at least this deep are located nearby. Given their size  and location, there is a strong case for arguing that they represent  burial areas.My research has been designed to respect both the historical  and scientific potential of the site as well as its religious and  commemorative significance.Geophysical tools
- Ground-penetrating radar (above) - sends pulses of radar into the earth and records the reflections
- Resistance survey - electric current passed through the ground via probes, with solid features exhibiting higher resistance than water-rich ones
- Electrical imaging - like resistance survey, but with multiple (eg 20) probes
No excavation was carried out and the ground was not disturbed, which would be a violation of Jewish law and tradition, banning the exhumation of the dead.Until relatively recently the technology has not been available to investigate the sites of the Holocaust in such a way.Aerial photography from the 1940s can now be supplemented with satellite imagery, GPS and mapping software.A range of geophysical surveying tools also exists, including ground penetrating radar, resistance survey and electrical imaging.However, no geophysical methods will reveal conclusively what is below the soil - they do not detect human remains.
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What each method does is to  highlight contrasts between the physical properties of the soil and  features within it, such as buried remains or ground disturbance.Conclusions can then be drawn about the nature of these  features by comparing historical and archaeological data, and drawing on  knowledge about construction, demolition and burial processes.As well as the pits, the survey has located features that  appear to be structural, and two of these are likely to be the remains  of the gas chambers.According to witnesses, these were the only structures in the death camp made of brick.Unlike at Auschwitz, there were no purpose-built crematoria at Treblinka.The decision to burn the bodies of victims was made only  after the camp had been operating for several months. The order to  exhume and cremate those already buried came in 1943, after the German  army had discovered the bodies of Polish officers massacred by the  Soviets at Katyn three years earlier - demonstrating to the German  leadership the importance of covering up its own crimes.Witness reports indicate that the bodies were burned on  improvised pyres made of railway lines and wood, and the ashes were  often reburied in the same graves the bodies had been taken from.Find out more
- The Hidden Graves of the Holocaust will be broadcast on Monday 23 January at 20:00 GMT on BBC Radio 4
Underground features detected here, coincide with variations in surface levelBut recent work in forensic cremation demonstrates that total eradication of bone requires extremely high temperatures. In most crematoria today, bones remain intact and have to be ground down to produce ash.At Treblinka it is clear that the ash contains many bones. Bone fragments can still be seen on the surface of the ground, especially after rain.Considerable evidence also exists to suggest that not all of the bodies were exhumed and cremated. Photographs show bodies littering the landscape as late as the early 1960s.But this work is just the beginning and further work is required to understand the complexity of the site.This initial survey should be viewed as a start of what will hopefully be a long-term collaboration between myself and the Treblinka museum, aimed at providing new insights into the physical evidence, and allowing the victims of the Holocaust to be appropriately commemorated.
Source:BBC
 
