Jihan, 24, rose to fame in a South Korean singing competition before turning to acting.
The two agencies representing the star - 935 Entertainment and 9Auto Entertainment - confirmed the news on Sunday.
Posting Black Square on Instagram, they wrote in a statement that they were
"heartbroken to be greeted with the sad news of his death" and told fans that Zihan "has become a star in the sky and has left us".
Expressing their "heartfelt condolences" to his family and all who loved him, they called him "a sweet and warm friend to all".
They also wrote of her "bright smile" and paid tribute to her "passion for acting", wishing her "last journey".
Jihan rose to fame in 2017 on the South Korean reality show Produce 101, where 101 K-pop hopefuls competed to win a spot in an 11-member boy band.
Despite not being a part of the final band - Wanna One - Jihan used the platform to break into acting,
starring in the South Korean high-school drama Today Was Another Nam Hyun Dae.
Former Production 101 contestants Park Heeseok, Kim Do-hyun and Cho Jin Hyung also paid tribute.
They wrote in a joint statement: "Ji Han has left this world to rest in peace. We bid him farewell on his final journey."
Funerals for the victims are already underway and the South Korean government has said it will help with funeral expenses.
According to AllKPop, Ji Han's funeral will be held on November 1st.
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