from Fritz Berg's:
Poison Gas Über Alles
The Soviet Origin of the Gas Van Story
The earliest reference to mass murder in gas vans that I have ever found is in July of 1943 when Pravda reported on the show trials of a number of German prisoners who had supposedly murdered Soviet citizens in Krasnodar with diesel powered vans. English translations of the Pravda stories appeared in The Trial in Britain through Hutchinson & Co., and Foreign Languages Publishing House we have the following text:
"In the autumn of 1942, the Germans began to use specially equipped automobiles which the population called 'murder vans,' for the purpose of doing away with Soviet citizens.
These 'murder vans' were covered five-ton or seven-ton gray-painted motor trucks, driven by Diesel engines."
For a later trial in Kharkov in December of 1943 we have in a publication called "The People's Verdict" the following information on page 43:
"The vans are lined inside with galvanized iron and have airtight folding doors at the back. The floor is equipped with a wooden grating under which passes a pipe with apertures. The pipe is connected to the exhaust pipe of the engine. The exhaust gases of the Diesel engine, containing highly concentrated carbon monoxide, enter the body of the van, causing rapid poisoning and asphyxiation of the people locked up in the van."
Of course, diesel exhaust never contains "highly concentrated carbon monoxide."
In a later publication entitled: "Soviet War Documents" from December 1943 and published by the Soviet Embassy in Washington, DC, we have a description of the gas van on page 172 which claims the engine was a "Sauer" engine and that the body of the van was constructed in Berlin. There is no Sauer engine manufacturer but there is a famous company called "Saurer." The connection that is made here to a company called "Sauer" is significant because it reappears in the infamous fake letter from Becker to Rauff in Nuremberg File PS-501. By their common errors one can often recognize the work of a forger. There is never any mention anywhere of the engines having been gasoline engines although that would have certainly made sense technically--nor is there any mention of producer gas wagons which would have made all the sense in the world.
for more on this: