The on-again, off-again girlfriend of US actor Jim Carrey has been found dead at her California home, with police believing she took her own life.

“Cathriona White, 30, was pronounced dead by paramedics Monday evening,” Fred Corral, a spokesman at the Los Angeles County coroner’s office, told AFP on Tuesday.

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He said White’s death was being treated as a suicide.

Local news reports said the couple, who have been dating on and off since 2012, broke up last Thursday.

White sent a cryptic message on her Twitter account that day that read: “Signing off Twitter, I hope I have been a light to my nearest and dearest.”

Carrey said in a statement that he was “deeply saddened by the passing of my sweet Cathriona.”

“She was a truly kind and delicate Irish flower, too sensitive for this soil, to whom loving and being loved was all that sparkled,” the 53-year-old actor added.

“My heart goes out to her family and friends and to everyone who loved and cared about her. We have all been hit with a lightning bolt.”

White was found at her home Monday evening by a friend who called emergency services. She had reportedly left behind a note.

Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14.