Remains of the Bab, Babi and Baha'i accounts

Bābī sources maintain, however, that the bodies were removed from the ditch through the efforts of a certain Ḥājī Solaymān Khān Mīlānī and eventually brought to Tehran, where they were buried in secret at the Emāmzāda Ḥasan, in which location some modern Bābīs believe them to remain (Nicolas, Sayyed Ali Mohammed, pp. 379–85). Bahaʾi accounts, however, state that the remains were at one point removed from the Emāmzāda on the instructions of Mīrzā Ḥosayn-ʿAlī Bahāʾ-Allāh (q.v.) and transferred from hiding-place to hiding-place for almost fifty years before being brought to Haifa in 1899.

(Denis MacEoin, The Messiah of Shiraz, p. 565)

Following is the official Baha'i narrative:

Just as Baha’u’llah was leaving Tihran, the sealed casket - containing the mortal remains of the Bab and Anis finally reached the capital. The hazardous journey from Tabriz had taken about ten months. It was solely due to Baha’u’llah’s initiative, and in strict obedience to His instructions, that the precious remains reached Tihran safely. As He left the city, Baha’u’llah gave instructions to Mirza Musa and one other believer to hide the casket in the shrine of the Imam Zadih-Hasan near Tihran. In the rising heat of summer, Baha’u’llah and two companions headed west towards ‘Iraq.

(Day of Glory, The Life of Baha’u’llah, by Mary Perkins, George Ronald, p 32)