Certain modern historians believe that some 43 members of the garrison were dead or missing for other reasons. Because so many non-combatants were present in the Fort when it fell, the number who died cannot be stated with any precision. 
The corpses were thrown into a ditch . Holwell and three others were sent as prisoners to Murshidabad, the rest of the survivors obtained their liberty after the victory of a relief expedition under Robert Clive. The Black Hole was later used as a waterhouse, and obelisk, 50ft. high, was erected in memory of the dead. 
The following description are obtained from 1911 Encyclopedia Britannica which portrays Holwell's ponit of view vividly;
The dungeon was a strongly barred room and was not intended for the confinement of more than two or three men at a time. There were only two windows, and a projecting veranda
outside and thick iron bars within impeded the ventilation, while fires raging in different parts of the Fort suggested an atmosphere of further oppressiveness. The prisoners were packed so tightly that the door was difficult to close.
One of the soldiers stationed in the veranda was offered 1,000 rupees to have them removed to a larger room. He went away, but returned saying it was impossible. The bribe was then doubled, and he made second attempt with a like result, the Nawab was asleep and no one dared wake him.
By nine o'clock several had died, and many more were delirious. A frantic cry for water now became general, and one of the guards, more compassionate than his fellows, caused some to be brought to the bars, where Mr. Holwell and two or three others received it in their hats, and passed it on to the men behind. In their impatience to secure it nearly all was spilt, and little they drank seemed only to increase their thirst. Self-control was soon lost, those in remote parts of the room struggled to reach the window, and a fearful turnult ensued, in which the weakest were trampled or pressed to death. They raved, fought, prayed, blaspherned, and many then fell exhausted on the floor, where suffocation put an end their torments.
About 11 o'clock the prisoners began to drop off fast. At length, at six in the morning, Siraj-ud-Daulah awoke, and ordered the door to be opened. Of the 146 only 23, including Mr. Holwell remained alive. and they were either stupefied or raving. Fresh air soon received them, and the commander was then taken before the nawab, who expressed no regret for what had occurred, and gave no other sign of sympathy than ordering the Englishman a chair and a glass of water . Notwithstanding this indifference, Mr. Holwell and some others acquit him of any intention of causing the catastrophe , and ascribe it to the malice of certain inferior officers, but many think this opinion unfounded. 
