A page from "The Night Hamburg Died", Martin Caidin, Four Square/New English Library, London, 1966. Originally published in USA by Ballatine Books, Inc, 1960

The text below the picture reads:

These victims-spared the direct effect of flames-died early in the firestorm from the combined effects of heat, carbon monoxide and suffocation. In many shelters the heat became so great that the corpses, as well as glass and metal, melted into blobs. National Fire Protection Association

(Note that Caidin has worked for US "intelligence":

In Japan for two years with the Intelligence and Public Information offices of the U.S. 5th Air Force, Mr. Caidin toured the devastated Japanese cities, and spent much time in Hiroshima, where the world's first atomic bomb used in the war was dropped.