Backstreet Boys' pop comeback has hit a stumbling block - singer A.J. Mclean has reportedly returned to rehab to conquer his drug and alcohol demons once and for all.
The singer has battled addiction for years and enrolled in treatment programs in both 2001 and 2002 for alcohol and cocaine abuse.
But a source tells TMZ.com McLean has struggled with sobriety in recent months and is now "out of control", threatening to derail the group's plans to hit the road for their upcoming joint tour with New Kids on the Block.
A spokesperson for the singer had yet to comment on the report as WENN went to press.
However, McLean appeared to reference to his return to rehab in a post on Twitter on January 9 - the same day he celebrated his 33rd birthday.
He wrote: "I love u all and wish me luck! I start my sober journey tomm (sic)!"
On January 10, he added, "See u on the other side!"