The CODOH Revisionist Forum

I'm putting this here as totally uncorroborated so far, but...

On August 17, 1944, Colonel Trapeznikov, head of the 65th Army’s SMERSH counter-intelligence department, reported to General Vadis about a camp the Germans had specifically built for the mass extermination of the population—primarily Poles and Jews. Counter-intelligence officers interviewed witnesses, including Jan Wernis—author of the pamphlet *A Year in Treblinka*—who had worked as a carpenter at the camp. The Military Council of the 65th Army established a commission to investigate these atrocities.

- Source

Original Russian:

Spoiler

17 августа 1944 года начальник ОКР "Смерш" 65-й армии полковник Трапезников доложил генералу Вадису о лагере, который немцы специально построили для массового истребления главным образом польского и еврейского населения. Контрразведчики опросили свидетелей, включая автора брошюры "Год в Треблинке" Яна Верниса, который работал плотником в лагере. Военный совет 65-й армии создал комиссию для расследования злодеяний.

I don't think Wiernik was interviewed by SMERSH, but August 15-17 was the date of some of the earliest Soviet interrogations related to Treblinka I and II. The earliest SMERSH report on Treblinka I know of is dated September 17 and doesn't mention Wiernik. But SMERSH certainly could have had a copy and Russian translation of Wiernik's book by August 17.

This Russian website could have garbled details, but worth checking if the SMERSH Trawniki guard interrogation reports ever surface online.