Dolores O'Riordan, lead singer of The Cranberries, died of fentanyl poisoning on Monday, a source in the London Police Department said.

Authorities found counterfeit fentanyl near the 46-year-old's rocker's bed, a source told the Santa Monica Observer. The source added that no official cause of death has been declared yet, saying that an official cause of death will be announced later with the toxicology report.

The source also added that suicide and a deliberate overdose are suspected.

Police ruled O'Riordan's death non-suspicious, meaning they found no evidence of foul play.

After splitting from her husband of 20 years in 2014, O'Riordan's life took a hard personal turn. The Irish singer spoke publicly about suicide and her bipolar disorder, which she said she was diagnosed with in 2015 and said she'd struggled with the symptoms for years.

In 2014, she told the Belfast Telegraph that she once tried to take her own life. “I tried to overdose last year... I suppose I am meant to stay here for the kids,” she said at the time.

She is survived by three children: Taylor Baxter, 20, and Molly Leigh, 16, and Dakota Rain, 12.

During the interview, the “Zombie” singer said she had to be careful not to keep sleeping tablets around “because if I have a few drinks I’ll take them…. Then you don’t wake up.”

In November 2014, O'Riordan was arrested and charged in connection with air rage on an Aer Lingus flight from New York to Shannon, Ireland. During the flight she reportedly grew verbally and physically abusive with crew. When police were arresting her after landing, she resisted, headbutting one and spitting at another. Later she told the media that she had been stressed from living in New York hotels following the end of her 20-year marriage.

The Cranberries cited O'Riordan's ongoing "back problem" as the reason for canceling the second part of the group's 2017 European tour and all of the group's North American tour. In late 2017, O'Riordan said she was recovering and performed at a private event.

It's unclear how significant, if at all, O'Riordan's back problem was in relation to her sudden death.

Her management group and the band have confirmed her death.

"Irish and international singer Dolores O’Riordan has died suddenly in London today. She was 46 years old," her PR agency said Monday, which was repeated on the band’s social media accounts. "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."

“Family members are devastated to hear the breaking news and have requested privacy at this very difficult time,” the statement continued.

In dying of Fentanyl overdose, O'Riordan joins other artists like Lil Peep and Prince.

Celebrities like James Corden, Josh Groban, Irish singer-songwriter Hozier and the Irish band Kodaline all expressed their sympathies at the news.

"My first time hearing Dolores O'Riordan's voice was unforgettable. It threw into question what a voice could sound like in that context of Rock," Hozier wrote on Twitter. "I'd never heard somebody use their instrument in that way. Shocked and saddened to hear of her passing, thoughts are with her family."

O’Riordan led The Cranberries to worldwide rock stardom in the 1990s, crafting hits like “Zombie,” “Linger” and “Dreams.” Altogether, The Cranberries sold over 40 million records worldwide.

The band's music sales have risen 900,000% since her death.