Wilmette police spokesman Eric Peterson said Monday that O'Connor has been located, though he wouldn't say where she was found.
But he says the singer "is safe and no longer considered a missing or endangered person."
Wilmette police confirmed O'Connor went on a bike ride Sunday at 6 a.m. and did not return. She was reported located around 2 p.m. Monday.
A caller to Wilmette police asked for authorities to check on O'Connor's well-being check after she failed to return.
Police refused to release any further information.
Two hours after O'Connor went on her bike ride, her official Facebook page had a vague, rambling post added to it:
It's unclear what the post means.
It's unknown why O'Connor was in the north suburbs last weekend. O'Connor performed with Buddy Guy in January. She was also at Metro Chicago on the North Side in March. She was performing in honor of the owner Joseph Shanahan.
Earlier this month, Arsenio Hall filed a $5 million defamation lawsuit against O'Connor for claiming that the comedian supplied drugs to Prince.
The lawsuit calls O'Connor's accusations "despicable, fabricated lies" and adds that "O'Connor is now known perhaps as much for her bizarre, unhinged Internet rants as for her music."
O'Connor, whose biggest hit was a 1990 reworking of the Prince song "Nothing Compares 2 U," posted on her Facebook page about a week after Prince's death that he was a "long time hard drug user."
"Two words for the DEA investigating where prince got his drugs over the decades.... Arsenio Hall," O'Connor posted on May 2.
She added: "Arsenio I've reported you to the Carver County Sherrif's office. Expect their call. They are aware you spiked me years ago at Eddie murphy's house."
Hall's suit filed in Los Angeles Superior Court said he had "minimal contact" with O'Connor, last seeing her 25 years ago. He said he never supplied illegal drugs to Prince and did not spike O'Connor with drugs either.
The lawsuit also claims that O'Connor only met Prince a few times and "detested" him and "spat on him quite a bit," so was in no position to know about anyone supplying drugs to him.
The Associated Press contributed to this report.