There's a html version of DTH. If the page numbers are the same, This is from 'The Treblinka Holocaust' by Naufmaier:
http://www.vho.org/GB/Books/dth/fndtreb.html
2.3. The Origin of the Current Version of Treblinka
Treblinka II was situated in an area by no means particularly remote and it concealed few secrets. The train line leading from the village of Treblinka to Siedlce ran at a distance of all of 300 meters from the camp, parallel to the nearby road; scarcely two kilometers separated the camp from the hamlets of Wólka Okraglik in the east and Grady and Poniatowo in the west.[47] If one credits the testimony of eyewitnesses, lively contacts even existed between the camp inmates and the local populace, with which a flourishing barter trade flourished.[48] In fact, soon after the opening of the camp (July 23, 1942), information from it was reaching the outer world. This was essentially coming from Jews who had run away from Treblinka, from the populace which resided in the area surrounding the camp, as well as from the Polish railway workers who operated the trains with the deportees. In these reports, the following methods of killing were mentioned:
Exhaust gases of a motor in whose fuel "toxic substances" had been mixed (Report of the Polish underground newspaper Informacja bieżąca, October 5, 1942[49]).
A gas with a delayed effect, which enabled the victims to leave the gas chamber and walk to the mass graves; there they lost consciousness and fell into the graves (Informaca Bieżąca, September 8, 1942.[50]
A mobile gas chamber, which moved along the mass graves and unloaded the bodies into them (Informacja bieżąca, August 17, 1942).[51]
Shooting with machine guns (Report of the Resistance to the Polish government-in-exile in London, March 31, 1943).[52]
Quick lime in the trains; the deportees arrived in Treblinka as corpses and were buried there (further report of the Resistance to the Polish government-in-exile, March 31, 1943).[52]
Electric current ("Ghetto Chronicle" of Emmanuel Ringelblum, entry for October 15, 1942).[53]
Hot steam. This murder method was described in several reports and dominated propaganda concerning Treblinka up into 1944. Of capital importance in connection with this is an unusually detailed report dating from 15 November 1942, from the resistance movement of the Warsaw Ghetto with the title Likwidacja żydowskiej Warszawy (Liquidation of Jewish Warsaw), in which mass killing by means of steam is described as follows:[54]