Whitney Houston performs at the Pre-Grammy Gala & Salute to Industry Icons with Clive Davis honoring David Geffen held in Beverly Hills, California, February 12, 2011.[Photo/Agencies]

Singer Whitney Houston is undergoing treatment again for drug and alcohol addiction, her spokeswoman said on Monday.

The multiple Grammy Award-winning diva has enrolled in an out-patient program rather than a residential facility.

"Whitney Houston is currently in an out-patient rehab program for drug and alcohol treatment. Whitney voluntarily entered the program to support her long-standing recovery process," publicist Jill Fritzo said.

Houston, 47, one of the top-selling female artists of all time with hits like "I Will Always Love You", launched a comeback in late 2009 after battling drug addiction for years. But her performances on some legs of her 2010 concert tour proved troubling.

In the opening leg of her British tour a year ago, she appeared short of breath. In Paris she was hospitalized with a respiratory infection and postponed several dates. And in Australia she was panned by fans and critics.

In April 2010, she called media reports that she was using drugs again "ridiculous".

Celebrity website TMZ.com said on Monday that Houston enrolled in the rehab program about 10 days ago, and is allowed to go out in public as long as she has a monitor.

TMZ cited an unidentified source as saying Houston was cleansing her system to get ready for a new movie. Details were not available.