SOURCE: BBC News (1-29-10)
Gandhi's grand-daughter, Ela Gandhi, told the BBC that a family friend had kept the ashes for decades. They were handed over to the family last year.
After Gandhi was assassinated 62 years ago, his ashes were distributed among family, friends and followers.
Ashes are customarily scattered over a body of water shortly after cremation.
These ashes will be scattered at sea exactly 62 years after his death.
Boats carrying about 200 family members and friends will be joined by South African navy vessels in the sea near Durban for the ceremony, Ms Gandhi, who lives in Durban, said.
Correspondents say it is difficult to estimate how many people received a portion of Gandhi's ashes after he was cremated in 1948.
The majority would probably have been scattered in a river or at sea shortly afterwards, according to Hindu custom.
"A family friend, Vilas Mehta, decided to keep some of Gandhi's ashes as a memento, not realising that according to Hindu customs they should be immersed," Ms Gandhi told the BBC.
She handed over a "little silver container" to her daughter-in-law on her death bed and told her to "keep it very safe".
"The daughter-in-law thought the family should have the ashes and she brought it to us last year.
"We started thinking - what shall we do with it? We had a couple of options. But then our broader family said, the ashes must be immersed."
In 2008, some of Gandhi's ashes, kept for years by an estranged son, were donated to a museum in Mumbai which arranged a ceremony to scatter them in the Arabian sea.
Mahatma Gandhi was assassinated by a Hindu fanatic on 30 January 1948.
Gandhi made South Africa his home for 21 years, working as a lawyer and activist.