GREEN DAY‘s label boss has described Billie Joe Armstrong’s visit to rehab as “no joke.”

The frontman checked in for treatment over substance abuse issues after an onstage meltdown in Las Vegas.

Warner Bros chairman Rob Cavallo, who used to produce GREEN DAY records, says:

“He’s under medical supervision for a while. His doctors are still evaluating. I don’t know if we’ll see him before Christmas – it’s undetermined when he’ll be back.”

GREEN DAY are scheduled to commence a US tour in November. Metallica have been announced as their replacement for the Voodoo Experience in New Orleans on October 27.