Actress Mya-Lecia Naylor, who starred in CBBC's Millie Inbetween and Almost Never, has died aged 16.
Her agents said she died on 7 April.
A statement posted to the CBBC website said: "We are so sorry to have to tell you that Mya-Lecia, who you will know from Millie Inbetween and Almost Never has, very sadly, died.
"Mya-Lecia was a much loved part of the BBC Children's family, and a hugely talented actress, singer and dancer.
"We will miss her enormously and we are sure that you will want to join us in sending all our love to her family and friends.
"We know this news is very upsetting, and it may help to share how you are feeling with friends or a trusted adult.
"If you are struggling and there is no one you feel you can talk to about it, you can call Childline on 0800 11 11."
A&J Management tweeted: "It is with the deepest sorrow we have to announce that on Sunday 7th April Mya-Lecia Naylor, very sadly, died. Mya-Lecia was hugely talented and a big part of A&J, we will miss her greatly.
"Our love and thoughts are with all her family and friends at this difficult time."
Among those to pay tribute was actor Emily Atack, who starred alongside her in Almost Never.
On Instagram she wrote: "So shocked and sad to hear about lovely Mya-Lecia Naylor. She was a beautiful and talented girl.
"A complete joy to be around on the set of Almost Never. Sending all my love to her family & friends. Rest in peace beautiful girl."
Alice Webb, director of BBC Children's which includes CBBC, said: "We are distraught and so terribly sad to hear the news about Mya.
"She has shone so brightly on our screens, both in Millie Inbetween and Almost Never, and it's unthinkable that she won't be part of our journey going forward.
"She was hugely popular with our audience, a very talented actress, dancer and singer, and a real role model for her young fans."
Mya-Lecia was also in Cloud Atlas and in one episode of Absolutely Fabulous.
© Sky News 2019