We shiites believe that his excellency Mahdi has two kind of occultation: Minor occultation and Major occultation. In the minor occultation, his honor was in contact with people by four elected deputies and after the death of fourth deputy, the major occultation has been started. These four elected deputies are as follows:
1- Uthman ibn Sa'id al-Asadi
2- Abu Jafar Muhammad ibn Uthman
3- Abul Qasim Husayn ibn Ruh al-Nawbakhti
4- Abul Hasan Ali ibn Muhammad al-Samarri
The deputyship of these people was general and absolute. Of course in that time, in special cases and in various cities, there were other people who undertook the deputyship of Imam that some believe this deputyship was without intermediating of elected deputies. Among these people Ahmad ibn Hamzah ibn al-Yasa', Muhammad ibn Ibrahim ibn Mahziar, Muhammad ibn Salih and Abu Muhammad Wajinayi can be named.
His excellency Mahdi, by a letter to Ali ibn Muhammad, notified about the beginning of major occultation this way:
In the name of Allah, the Compassionate the Merciful
O Ali ibn Muhammad al-Samarri! May Allah increase the reward of your brothers concerning you (i.e. your demise)! Death will come to you within the next six days. So complete your works and do not nominate any person after you. The sequence of special deputies will come to an end and the Major Occultation will commence with your demise.
Now the reappearance will occur only with the permission of Allah, after a prolonged period and after the hearts of people are hardened. And such a period will emerge on my Shias when people will claim that they have seen me. Whoever makes such a claim before the advent of Sufyani and the heavenly voice, is a liar, an impostor. There is no strength and power same that of Allah, the High, the Great.
Al-Ghaybah, Shaykh Tusi, page 395
What is the opinion of Mansoor Hashemi Khorasani about this case?
Also, what is the opinion of his honor about Minor advent and Major advent in which we shiites believe?