Tributes have been paid to pop star, Simone Battle, who has died at the age of 25.

Simone's G.R.L. bandmates, Paula Van Oppen, Lauren Bennett, Emmalyn Estrada and Natasha Slayton, took to Twitter to express their shock and grief.

"Words cannot express the depth of our loss", a post on the band's official account reads.

"Simone's incredible talent was only surpassed by the size of her heart.

"We will carry her memory with us in everything we do."

Words cannot express the depth of our loss. Simone's incredible talent was only surpassed by the size of her heart.

— G.R.L. (@grl) September 6, 2014

We will carry her memory with us in everything we do.

— G.R.L. (@grl) September 6, 2014

Simone was reportedly found dead at her home in LA on Friday morning (5 September).

The singer's death was confirmed with the release of a statement from the band's record label and management team yesterday (6 September).

Battle appeared in the debut season of the US X Factor in 2011, and was mentored by judge and franchise creator Simon Cowell.

After releasing her own single, she joined G.R.L., founded by Pussycat Dolls creator Robin Antin.

Simon Cowell took to Twitter last night to pay tribute to his former mentee.

I am so sad to hear about the news Simone Battle has passed away. She was such a fun nice person. It's such a loss. Rest in peace Simone.

— Simon Cowell (@SimonCowell) September 6, 2014

"I am so sad to hear about the news Simone Battle has passed away. She was such a fun, nice person. It's such a loss.

"Rest in peace Simone," the music mogul added.

Ex-PCD member Kimberly Wyatt also paid her respects to Simone's loved ones after hearing the news.

"In disbelief #RIPSimone", the star tweeted, "Been loving @grl #UglyHeart, [Simone] was so talented. My heart hurts for her friends, family and band mates."

She later shared a performance from Simone's audition at judge's houses during the 2011 season of the reality show, writing: "In light of the struggle, this hits hard".

In light of the struggle this hits hard: Simone Battle -X Factor U.S. - Judges House: http://t.co/DE5KLjsgXj #RIPSimone

— Kimberly Wyatt (@KimberlyKWyatt) September 6, 2014

Cheryl Fernandez-Versini also paid tribute to the pop star via her account.

"Such tragically sad news to hear of the passing of Simone Battle... My thought and prayers are with her loved ones", she tweeted.

Such tragically sad news to hear of the passing of Simone battle.. My thoughts and prayers are with her loved ones #RIPSimone

— Cheryl (@CherylOfficial) September 6, 2014

Girlband Neon Junglepaid condolence to the singer's death, tweeting: "just read the terrible news that Simone Battle has passed away.

"Sending all our love to her family and [the] rest of @grl. May her soul RIP."

The cause of her death is still being investigated.