Not only was the pharaoh's outer sarcophagus huge but the fact that he used four of them, made of stone, is unusual. "Merneptah's unique in having been provided with four stone sarcophagi to enclose his mummified coffined remains," said Brock in his presentation. [The 10 Weirdest Ways We Deal With the Dead]
Within the outer sarcophagus was a second granite sarcophagus box with a cartouche-shaped oval lid that depicts Merneptah. Within that was a third sarcophagus that was taken out and reused in antiquity by another ruler named Psusennes I. Within this was a fourth sarcophagus, made of travertine (a form of limestone), that originally held the mummy of Merneptah.
Only a few fragments of this last box survive today; the mummy itself was reburied in antiquity after the tomb was robbed more than 3,000 years ago. It was after this robbery that the outer sarcophagus box, and the second box within it, were broken apart (the lids for both boxes being kept intact). They were destroyed not only for their parts but also to help get at the third box (that was reused by Psusennes).
Fire was used in breaking apart the outer sarcophagus box.
"Scorch marks, spalling [splinters] and circular cracking on various locations of the interior and exterior of the box attest to the use of fire to heat parts of the box, followed by rapid cooling with water to weaken the granite," writes Brock in his symposium abstract, adding that dolerite hammer stones also appear to have been used.