Dolores O’Riordan, the lead singer with the Irish band The Cranberries, died suddenly on Monday at the age of 46, The Guardian reported. The cause of death is yet unknown.

O’Riordan was in London for a recording session when she was found dead at her hotel. “At this early stage the death is being treated as unexplained,” a statement by the London Metropolitan Police said.

“The lead singer with the Irish band The Cranberries was in London for a short recording session. No further details are available at this time,” a statement by O’Riordan’s publicist said according to BBC.

Noel Hogan, Fergal Lawler and Mike Hogan – O’Riordan’s current band mates – paid tribute to her on Twitter.

The Cranberries became famous with their 1993 debut album Everybody Else Is Doing It, So Why Can’t We? and had sold over four crore records worldwide until 2017.

In 2017 The Cranberries announced a tour of Europe and the United States. However, in May, the group had to cancel its ongoing European tour due to O’Riordan’s poor health. The Cranberries website cited “medical reasons associated with a back problem” preventing singer Dolores O’Riordan from performing.