Irish singer-songwriter Sinead O'Connor has been found safe after police in suburban Chicago received a report that she had not returned from a bike ride a day earlier.
Wilmette police spokesman Eric Peterson said on Monday O'Connor had been located, "is safe and no longer considered a missing or endangered person", though he wouldn't say where she was found or release details about her condition.
Local police issued a well-being check for O'Connor earlier on Monday, saying someone called to report that she hadn't been seen since leaving for a bicycle ride early on Sunday morning.
It's unclear why O'Connor was in Wilmette, an upper-class suburb about 24km north of Chicago along Lake Michigan.
Police say she reportedly left for her bike ride at 6am on Sunday. About two hours later, a rambling message was posted on her official Facebook page that cited an upcoming court hearing and a child custody dispute.
On Friday, a long message posted as an "open letter to my son Shane" encouraged the 12-year-old to bring his own case against Tusla, a child welfare agency in Ireland.
O'Connor was sued this month by comedian Arsenio Hall over a Facebook post that stated investigators looking into the supplier of drugs used by Prince should question Hall. She also accused him of drugging her. The lawsuit seeks $US5 million ($A6.86 million).
And in November, she posted a message on Facebook saying she had taken an overdose at a hotel somewhere in Ireland. Irish police later said she had been found safe.
The next month, O'Connor posted on Facebook that she had been detained in a hospital for mental health evaluation.
The gifted but troubled singer-songwriter's rendition of Nothing Compares 2 U topped charts from Europe to Australia, and earned O'Connor multiple Grammy Award nominations. In 1991, O'Connor was named Artist of the Year by Rolling Stone.
But her blunt-spoken manner often drew criticism, especially in the US. In 1990, some US radio stations refused to play her music after she banned the Star-Spangled Banner from her show in New Jersey.
She drew intense criticism in 1992 when she ripped up a picture of Pope John Paul II on Saturday Night Live.
O'Connor, who was diagnosed with bipolar disorder more than a decade ago, has spoken of her mental health problems.
She told Oprah Winfrey in 2007 that before her diagnosis she had struggled with thoughts of suicide and overwhelming fear. She said at the time that medication had helped her find more balance, but "it's a work in progress".
In 2012, O'Connor cancelled a planned tour, saying she her doctor had told her to rest after a "very serious breakdown".
Over the years, O'Connor has voiced support for other young female performers facing intense public scrutiny, including Britney Spears and Miley Cyrus. O'Connor - who has been married four times and has four children - signed a deal in 2014 to write a memoir.
