(Cover) - EN Showbiz - Mark Ronson has lost his "musical soulmate", as tributes pour in following the death of Amy Winehouse.

The 35-year-old music producer created most of the late 27-year-old's Grammy-winning album Back to Black. He took to his social networking site to express his grief at the loss of the talented star.

"She was my musical soulmate and like a sister to me (sic)," he tweeted.

"This is one of the saddest days of my life."

The British DJ, 35, worked with Amy on the album in 2007. The following year, the record won five Grammy Awards, including Producer of the Year.

Kelly Osbourne also took to Twitter to express her sadness at the loss of her friend. The British TV personality, 26, revealed that she was struggling to cope with the news.

"I can't even breath right my now. I'm crying so hard (sic) "she said."I just lost one of my best friends. I love you forever Amy and will never forget the real you!"

Amy's dad Mitch Winehouse was spotted at JFK just hours following his daughter's death.

He was reportedly in the first class lounge, "pacing up and down as he talked on his cell phone," a source told TMZ.

He was scheduled to perform at the Blue Note in New York City, but cancelled the performance, following news of his daughter's death.

Amy was found dead at her London apartment yesterday afternoon.

The troubled British singer, who had a long-running battle with drugs and alcohol, was discovered in Camden, North London, after the London Ambulance Service was called to the property.

A spokesperson for Metropolitan Police confirmed a 27-year-old woman had died, adding they are treating the death as "unexplained". (C) Cover Media