Cranberries singer Dolores O'Riordan File picture: Niall Carson/PA via AP

London - Police say they are not treating the death of Cranberries singer Dolores O'Riordan as suspicious.

O'Riordan was found dead Monday morning at a London hotel. Police initially called the death "unexplained," but said Tuesday that nothing suspicious had been found. The case is being passed to a coroner to determine the cause of death.

O'Riordan had suffered mental and physical health problems over the years. The Cranberries cut short a world tour in 2017 because of the singer's back problems.

The 46-year-old Irish singer was in London to record vocals for a cover of The Cranberries' hit "Zombie" by Los Angeles rock band Bad Wolves.

Read: Cranberries mourn 'true artist' Dolores O'Riordan

Dan Waite of music label Eleven Seven said O'Riordan left him a voice message early Monday saying she was looking forward to the recording. He said "she sounded full of life, was joking and excited to see me and my wife this week."

Lead singer Dolores O'Riordan from The Cranberries performs onstage during a benefit show in aid of the United Nations UNHCR refugees fund held at the Royal Albert Hall, central London. File picture: Yui Mok/PA via AP

"The news of her passing is devastating and my thoughts are with Don, her ex-husband, her children, and her mother," Waite said.

Also read: Cranberries singer Dolores O'Riordan dies aged 46

The Cranberries formed in Limerick at the end of the 1980s and had international hits in the 90s with songs including "Dream," ''Linger" and "Zombie."

Irish Prime Minister Leo Varadkar said that "for anyone who grew up in Ireland in the 1990s, Dolores O'Riordan was the voice of a generation."