Glee Season 4 finale may have to be filmed without Cory Monteith, who plays Finn Hudson in the hit show choir dramedy. Reports indicate Monteith has voluntarily gone back to rehab for substance addiction.

Monteith "has voluntarily admitted himself to a treatment facility for substance addiction," the actor's rep confirmed on Easter Sunday. Lea Michele, the actor's girlfriend on and off screen, expressed support for Monteith, saying, "I love and support Cory and will stand by him through this."

On Glee Season 4, Finn rushed to New York from Lima, Ohio to save Michele's character from a potentially damaging relationship with a male prostitute. Fans of the couple lovingly call them Finchel, to ship their characters Finn and Rachel.

Speaking to People magazine, Michele added, "I am grateful and proud he made this decision."

Glee series creator Ryan Murphy has also said he is behind the actor 100 per cent. On Twitter, the showrunner shouted out, "I am so proud of Cory Monteith and love and support him 100 [per cent]."

On the same social network, Monteith himself hinted the news should be taken positively. "Such a beautiful day! Truly seeing the forest for the trees. #gratitude," he tweeted on Friday. Monteith was much younger the first he had gone to rehab.

"I don't want kids to think it's okay to drop out of school and get high, and they'll be famous actors, too," Monteith told People magazine in June two years ago.

Entertainment news site Deadline reported Glee Season 4 finale will touch on Finn's absence. This is the first time the Finchel pair will not be at the center of the Glee finale stories.

Monteith "graciously asks for your respect and privacy as he takes the necessary steps towards recovery," the actor's rep told the media.

Meanwhile, American Idol 2012 runner-up Jessica Sanchez will appear in two Glee 4 episodes, including the finale, which Fox will air in May.

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