The Busan-born icon became a child star, with Sulli - real name Choi Jin-ri - first gaining success as an actress.
"So far, it seems she killed herself, but we will leave all possibilities open and investigate.""Going braless is one's freedom", she said on Korean network JTBC's Night of Hate Comments show on 21 July.
Korean pop star Sulli was found dead at her home near Seoul on Monday.
Former member of f (x) Amber Liu has suspended all upcoming activities following the death of former bandmate Sulli.
We apologize for conveying such sad and unfortunate news.
Sulli had nearly six million followers on Instagram and sparked controversy in conservative South Korea with her outspoken views on feminism and for refusing to wear a bra.
Sulli has left our side.
'We can not believe the situation now and we are just filled with grief. "We express our deep condolences".
She started her career in 2009 as a member of f (x) before leaving six years later to pursue her passion for acting, starring in TV dramas and films. In 2014, she took a hiatus from the entertainment industry due to mental and physical exhaustion.
She said then that she was mentally and physically exhausted after suffering from malicious comments and false rumours online.
Controversy: Sulli's outspoken nature made her the subject of controversy among her fans, as when revealing photos of her surfaced on social media in recent years. This caused uproar in the traditionally conservative South Korea. "I hope people are checking up on them & making sure they're alright...", a fan tweeted.