Production on Maze Runner: The Death Cure, the third entry in the postapocalyptic series, was set to resume in May, but has been postponed again while O'Brien recovers, according to Entertainment Weekly.
"His injuries are very serious and he needs more time to recover," publicist Jennifer Allen said in a statement to EW.
Twentieth Century Fox, the studio behind Maze Runner, said in its own statement to EW: "The resumption of principal photography on Maze Runner: The Death Cure has been further delayed to allow Dylan O'Brien more time to fully recover from his injuries.
"We wish Dylan a speedy recovery and look forward to restarting production as soon as possible."
O'Brien, 24, was hospitalized with multiple injuries following an accident on the Vancouver, Canada, set.
He was reportedly "in a harness on top of a moving vehicle when he was pulled off the vehicle unexpectedly and hit by another vehicle," sources told The Hollywood Reporter. O'Brien suffered a "concussion, facial fracture and lacerations," according to THR, citing a report from regulatory agency WorkSafeBC.
Soon after the accident, director Wes Ball took to Twitter to apologize "for the grief this accident has caused his friends and family as well as my wonderful cast and crew."
"Well, it's been a whirlwind of emotions these past few days," Ball wrote in a handwritten letter he tweeted. "I've been overwhelmed with feelings of anger and sadness and guilt. But, ultimately I find myself left with a deep love and respect for Dylan. He is one tough cookie."