The key text was published by Comte Beugnot, Les Olim ou registres des arrets rendus par la cour du roi, sous les r¸gnes de Saint Louis et de Philippe-le-Hardi, I, Paris, 1839, 71.
The dean and chapter of Amiens complained that on the night when the cathedral was burned, a certain chest containing the church's seals and privileges placed within the wall of the same church was taken from that place and broken and carried away, and the afore-mentioned seals and privileges were stealthily removed, begging the the lord king to give his counsel on this. Through the royal inquest that was then made, the three suspects named below were found, that is Robertus Bisaharz, who did much damage to the church that night; Ansellus [Anseau], sergeant of the city of Amiens, gravely suspected of having carried off and broken the said chest, and Injorrannus [Enguerran] de Croi was also found somewhat suspect. The king was decided to have the three taken prisoner by the bailiff of Amiens.
See also G. Durand, Monographie, I, 35-36 and Inventaire sommaire, V, iv.
Reference to the fire is also made in the opening lines of the Roman d'Abladane, see F. Lecoy, "Le roman d'Abladane," Romania, XCII, 1971, 458-506, esp. 475, "Or, escoutes que li boins clers maistres Richard de Fournival, chanchelier de l'Eglise Nostre Dame d'Amiens, et li autres maistres qui a ce temps estoient, virent et lurent ung livre, qui fust ars au derein feu de Nostre Dame d'Amiens en l'an de grace mil cclviii, le vigile de saint Firmin le confesseur..." J.-J. De Court, Memoires cronologiques, II, 3 "Nous avons vus dans plusieurs anciens M.S. qu'une partie de cette eglise fut brulee le dernier aoust 1258: sans autres circonstances, on pourroit conjecter que cet incendie arriva par la faute des ouvriers qui y travailloient encore." In a bull of July 18, 1262, Pope Urban IV, noting that "cum privilegia, instrumenta, littere ac munimenta ejusdem ecclesie, una cum ipsa ecclesia, peccatis exigentibus, sint combusta," charged Gilles de Vitri, dean of the chapter of Noyon Cathedral with the task of examining books and registers where the key documents of the Amiens chapter had been transcribed and with supervising the task of re-writing these documents in a form that would have the same authority as the lost originals, see G. Durand, Inventaire sommaire, V, iv, and Arch. Somme, G. 651.