Police are concerned for the welfare of Sinead O'Connor who has been missing for more than 24 hours.

The Nothing Compares 2 U singer has not been seen since 6am on Sunday when she went for a bicycle ride in Chicago.

Officers in the area said they are checking on her well-being.

In November last year O'Connor posted on Facebook that she had taken an overdose.

At the time a representative for the pop star was reported as saying she was "unwell and receiving treatment".