Sinead O'Connor was found safe in the Chicago suburbs on Monday, a day after the Irish singer set off alarm by not returning from a bicycle ride, police said.

Police in Wilmette, Illinois had voiced concern for the safety of O'Connor, who has worried many fans with recent Facebook postings that sounded suicidal.

Hours after the police issued an alert, which set off a flurry of concerned messages on social media, authorities said the 49-year-old had been found.

"Sinead O'Connor has been located. She is safe and is no longer listed as a missing/ endangered person," a police statement said.

A police spokesman declined to offer further details. The Wilmette Beacon newspaper reported that O'Connor had been staying in the suburb for several weeks with friends.

Police said that a caller had reached out to voice concern as the singer had not been heard from since Sunday at 6 am (1100 GMT) when she went on a bicycle ride.

Brian King, the local police chief, told the Chicago Tribune that O'Connor was riding a motorized bicycle and wearing a sweatshirt with "Ireland" written on the back.

Alarming Facebook messages

O'Connor, who has always been known for her strong views, has recently posted a string of messages on Facebook that have raised alarm.

In her latest posting, O'Connor appeared to be asking her son to go to court on Tuesday to take custody of his brother.

She also posted as her Facebook cover photo an image of US abolitionist hero Harriet Tubman with the quote: "I had reasoned that out in my mind, there was one of two things I had a right to, liberty or death; if I could not have one, I would have the other."

Late last year, she suggested on Facebook that she had tried to kill herself by overdosing.

O'Connor also recently wrote that comedian Arsenio Hall had been providing drugs for decades to late pop icon Prince, leading Hall to express outrage and sue for libel.

Prince, who died on April 21 in unclear circumstances, wrote O'Connor's best known song, the ballad "Nothing Compares 2 U."

O'Connor won critical acclaim for her haunting voice and intricate musical expression on her two first albums, "The Lion and the Cobra" and "I Do Not Want What I Haven't Got."

But she was also immediately controversial in the media. She took to task the pop culture's expectations of female sexuality by shaving her head and singing in shapeless clothes.

O'Connor, who said she was abused by her mother, has also been outspoken in criticizing the Roman Catholic Church for not doing more to protect children.

In one of her most polemical incidents, she ripped up a picture of then pope John Paul II when performing on US television's highly watched "Saturday Night Live" program in 1992.

While gradually retreating from the intense public spotlight, O'Connor has remained active and experimental as an artist.

She notably took a turn into reggae with her 2005 album "Throw Down Your Arms" after she moved to Jamaica and explored the Rastafarian faith.