The mother of a victim of one of Britain's most notorious killers died Saturday, a day after police said they were investigating a possible clue to where her child was buried nearly 50 years ago.

Winnie Johnson, whose 12-year-old son Keith Bennett went missing in 1964 in northern England, had spent the long decades since seeking first to find, and then to give a proper burial to, her murdered child.

But her death after serious illness has come before that hope could be realized.

Ian Brady, who was jailed for life in 1966 for three other child murders committed with the help of his partner Myra Hindley, admitted killing the boy in 1987 but has never disclosed the whereabouts of his body.

The other four victims were buried on Saddleworth Moor, a lonely upland expanse in the Pennine hills, near Manchester, but repeated searches have never uncovered Keith's remains.

Brady, known as the "Moors Murderer," remains in a secure psychiatric unit.

A statement on the family's website, Searching for Keith, confirmed that Johnson, a "much-loved mother, grandmother and great-grandmother," had died at age 78.

"Winnie fought tirelessly for decades to find Keith and give him a Christian burial," it said.

"Although this was not possible during her lifetime, we, her family, intend to continue this fight now for her and for Keith. We hope that the authorities and the public will support us in this."

Police revealed Friday that they were investigating claims that Brady may recently have given details of the burial spot to one of his longtime visitors, in a sealed letter to be passed to Johnson after Brady's death.