The nation is in three days of mourning for those thought to have perished at sea after the ferry left on a journey from the island of Nonouti to the capital Tarawa three weeks ago.
President Taneti Maamau declared a public holiday "as a solemn day of remembrance and to honour those who have lost their lives in this tragedy."
The official mourning period started yesterday.
The Kiribati government said the inquiry would carry out "fact-finding missions" and "comprehensive investigations".
