More than 55,000 migrants have died on their journey in the past 20 years and their families rarely learned of their fate, the International Organization of Migration (IOM) said on Tuesday.
In a report entitled "Fatal Journeys", the agency called on authorities to ensure the missing are identified and their families traced.
Of last year's deaths, 3,770 occurred in the Mediterranean where boats capsized en route to Europe. Others died in the Bay of Bengal and Andaman Sea, the Gulf of Aden and Red Sea and along the U.S.-Mexico border, it said.
"A second tragedy following the thousands of victims is that the majority, even among deaths that are known of, are never officially identified," IOM said. "For each body that remains nameless..., families are left wondering if their relative is alive or dead."
Without legal proof of death, it may be difficult for spouses to remarry or for families to inherit property.
Fewer than half of the 387 migrants who died when their boats capsized off the Italian island of Lampedusa in October 2013 have been officially identified, it said. In the United States, a cemetery in Arizona contains the remains of at least 800 unidentified individuals believed to be migrants.
Little is known either about the deaths of migrants travelling north overland from sub-Saharan Africa.
At present there is no established common practice for collecting information on migrant deaths between states, or even sometimes between different jurisdictions in the same country, the report said.
"Above all, international and regional databases are needed, in which data that is collected nationally can be stored securely and accessed transnationally," it said.