The news was confirmed by the Irish musician's publicist, Lindsey Holmes that O'Riordan passed away suddenly.
No cause of death has yet been announced, The Guardian reported.
O'Riordan had been in London for a recording session, after she cancelled a tour to Europe and North America with a reunited Cranberries last year because of a back problem.
The band released the acoustic album 'Something Else' in 2017.
"Family members are devastated to hear the breaking news and have requested privacy at this very difficult time," the statement added.
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"At this early stage the death is being treated as unexplained," the statement by the police read.
The Cranberries was formed Limerick, Ireland towards the end of the 1980s and the band shot to fame in the 1990s with blockbusters such as "Zombie" and "Linger".
O'Riordan, who was born in Limerick in 1971, was the chief lyricist and co-songwriter of the music group. Her wailing voice in the distinctive west Irish accent reverberates as strongly as the songs of the band.
The album was followed by an even bigger hit in 'No Need To Argue', that produced "Zombie", a torturous anthem laced with political overtones highlighting the violence of Northern Ireland's conflict in the 20th century called Troubles.
Before breaking up in 2003, the group had come up with three more studio albums. They, however, reunited in 2012 to release an LP titled "Roses".
As a solo artiste, O'Riordan released two albums - 'Are You Listening' (2007) and 'No Baggage' (2009).