Spade is survived by her husband of more than three decades, designer Andy Spade, and their 13-year-old daughter.
Officials are not authorised to divulge any additional information as the investigation into her death continues.
Actress Lucy Hale from Pretty Little Liars said "mental health does not discriminate and can happen to anyone with any circumstances", adding: "I hope she has found peace".
Spade, who was 55, created a line of sleek handbags in the early 1990s that created a smash.
Kate Spade New York has hundreds of stores across the U.S. and the world, including in Singapore.
The company was acquired by Neiman Marcus for $125 million in 2007 and Kate and Andy stepped away from day-to-day operations. Last year, the brand was purchased by Coach for US$2.4 billion (S$3.2 billion).
She sold the company in 2007 to focus on the couple's daughter Frances, who was born in February 2005.
Chelsea Clinton, Kenneth Cole, Josh Groban, Liz Lange and many more mourned Spade's death.
Spade received many prestigious awards, including the Council of Fashion Designers of America award for "America's New Fashion Talent in Accessories" in 2006. Her impact on the fashion and accessories world will forever be felt by those who knew her and those who were fans of her work. "We loved Kate dearly and will miss her terribly". Kate Spade Handbags was launched in 1993, with its first store located in Manhattan's SoHo neighbourhood.
A woman walks by the Kate Spade store in New York's Soho neighborhood, Tuesday, June 5, 2018.
"Fuzzy picture but i love it. Kate and I during Christmas family photos", David captioned the photo. In 2016, they launched a new fashion brand called Frances Valentine, which sells footwear and accessories.