L'Wren Scott, a designer and the girlfriend of Sir Mick Jagger, has been found dead in her New York City apartment. Scott, 49, was found at 10:00 local time (14:00 GMT) by her assistant, according to BBC News.

Police are treating it as a suicide, although the medical examiner has yet to determine an official cause of death.

A spokesman for Sir Mick said the singer was "completely shocked and devastated" by Scott's death.

Scott, born Luann Bambrough, was raised by adoptive parents in the U.S. state of Utah. She began her career as a model in Paris, then moved to Los Angeles to become a fashion stylist, according to a biography on her company's website.

She and Sir Mick, the singer of the Rolling Stones, began dating in 2001. She founded her own label in 2006.

Scott's death comes a month after she cancelled a show at London Fashion Week, saying production delays left key pieces unready for the show.

As news of her death spread, tributes rolled in from around the fashion world.

"Rest in peace, L'Wren Scott. You'll forever be missed," wrote Marc Jacobs on Twitter.

Steven Colb, chief executive officer of the Council of Fashion Designers of America, wrote, "So very sad today. L'Wren Scott was such a great talent and beautiful person. My thoughts are with her loved ones."