Pharrell Williams has led the tributes to "beautiful" singer Leah LaBelle, who died in a car accident with her ex-NBA star husband Rasual Butler.

LaBelle, who was an American Idol finalist in 2004, and former basketball player Butler were killed in a single-vehicle crash in Los Angeles on Wednesday.

Butler, 38, and LaBelle, 31, were pronounced dead at the scene after the Range Rover Butler was driving flipped over twice after hitting three parking meters and a wall, according to The Associated Press.

Producer Williams, who previously worked with R&B singer LaBelle when she signed to his record label, shared a collection of pictures of the two of them together on Instagram.

He wrote on Instagram: "@leahlabelle, your spirit was just as your voice; beautiful. Moments like these leave us with so many questions.

"What I don't question is how much you loved God, how much you love your life partner and where you guys are now. Sing Sis, sing."

Singer and The Voice UK coach Jennifer Hudson, who appeared on the same series of American Idol with LaBelle, said: "@leahlabelle it broke my heart, when I heard the news!

"The world lost a shining star! My prayers and thoughts are with your family! Rest In Peace."

Singer JoJo, who once toured with LaBelle, tweeted: "Leah. beautiful sister from another mister. You will NEVER EVER be forgotten. Your voice. Your spirit. Your light. Cannot comprehend what this loss means.

"Thinking about your unwavering faith in God brings me peace. I love you, forever angel."

Fantasia Barrino, who won the same series of American Idol LaBelle appeared in, said that she will "never forget" her in an emotional post."This just doesn't seem right even saying right now but Rest In Peace Baby Girl," she wrote.

After her stint on the US reality show for its third season, LaBelle went on to carve out a successful music career, notably on YouTube.

Her song Sexify is her most popular hit and has been watched more than one million times on the video platform.

Butler, who played in the NBA for 14 years, also received tributes following the fatal crash.

Retired professional basketball player Kobe Bryant tweeted: "Rest In Peace my brother #RasualButler."

The Los Angeles Clippers, for whom Butler previously played, said he "will long be remembered not only for his accomplishments on the court, but for his vibrant personality, positive outlook and the compassion he had for everyone around him".