Below is an article from the August 3, 1944 edition of Soviet War News Weekly, published by the Soviet Embassy in London. It was published at least a month prior to Grossman's visit to the site of the former German camps at Treblinka, which resulted in his famous article "The Hell of Treblinka," in which he claimed 3,000,000 "mainly Jews" had been killed by gas, steam, but mostly suction. Historian Antony Beevor has shown that Grossman excluded from the article an even wackier detail he'd written about it in April 1944.
In this article he puts the number of Nazi extermination camps in just Eastern Poland and Silesia at thirty plus, and introduces yet another death camp killing method. He does not specifically mention Treblinka by name, nor Belzec, just Lublin (Majdanek), and Sobibor, effectively twice, as Sobibor is just five miles south of Włodawa.
Reading this Grossman article you might be reminded of Boris Polevoi's later article about the electrocution conveyor belt of Auschwitz. Perhaps this is where he found some inspiration.
Conveyors in Death Factories
I have seen many tears in Poland. But I have seen no Jewish tears. There are no Jews in Poland. They have all been slaughtered, and their bodies burned to ashes. Lublin had the largest Jewish population in Poland—its Jewish citizens numbered over 40,000. In Lublin I saw not one Jewish man, woman or child.
We have heard about the death factories in Poland. People were told they were being taken to labour camps. They were packed into trains. Then the trains were switched to a spur line running to huge barracks.
The people were told to strip and go to bath-houses. There they were killed by lethal gases, or by electricity, or the floor opened up and they dropped into underground cellars where their bones were crushed, after which a conveyor ran the mutilated bodies into a furnace.
I was told there were more than thirty such death factories in Eastern Poland and Silesia. There was one six miles from Lublin, another near Sabibur station in the same area, another near Wladowa.