When the manager could not contact Goo Hara despite repeated phone calls, he went to her home.
He found the former member of South Korean girl group Kara unconscious on the floor.
There were reports by Korean media that smoke filled the room she was in.
Goo, 28, who was rushed to hospital early on Sunday (May 26), is said to be in a stable condition but has yet to regain consciousness.
Earlier, netizens voiced their concern after the singer posted messages on Saturday (May 25) that dwelled on issues of betrayal and self-doubt.
In one message, she revealed that she appeared "fine on the outside, but it feels as if I am starting to break into pieces inside".
Goo, who has appeared in TV dramas, has been in the news recently over her dispute with her former boyfriend Choi Jong-bum, 41.
She alleged that he assaulted and blackmailed her.
He, in turn, accused her of assault, releasing photographs of scratches on his face and saying that the injuries affected his job as a hairdresser.
In a hearing in April over charges that included threats to release sex videos, he said the bruises on her arms and legs resulted from his efforts to calm her down during a heated quarrel.
He denied that he had used photographs of Goo with bruises to force the chief executive of her agency to kneel before him.
Choi admitted, however, that he was responsible for property damage during the altercation.
Goo's hospitalisation has drawn sympathy from netizens.
One, justtryinghere, posted that the singer must have also been affected by some folk who called her an attention-seeker.
"I'm so happy someone heard her cries and got help quickly. This is heartbreaking. Taunted by her boyfriend, then taunted by the people she tried to warn about her pain.
"I really hope she has good and honest people around her to protect her going forward," the writer shared.
Another netizen, kpauburn, posted: "People should stop posting toxic stuff on her social media. She needs help, I hope she gets it and finds a way to live happily. I will pray for her."