A source told the New York Daily News that there was no foul play suspected "at this time."
No other details were immediately available.
"I'm absolutely shocked, for sure," fellow fitness personality Annette Milbers told the Daily News. "We messaged last week. She always made other people feel great, and she had reached out to me because I competed. She said how proud she was."
Blank was also a bodybuilder, becoming the youngest competitor to win the International Federation of Bodybuilding and Fitness World Championships in 1999.
When she was just 18 she placed 5th in World Fitness Olympia and soon after began making appearances in women's fitness and bodybuilding magazines.
She has worked with celebrities including Alex Rodriguez, Mickey Rourke and Jordana Brewster, according to her website.
Blank had one acting credit to her name as a "Female Body Builder" on Spin City in 2001, in a scene opposite Charlie Sheen.
She also appeared on the covers of Oxygen and MuscleMag and had her own online fitness program called the Body Blank Program.
Since her death was announced tributes have flowed on her social media pages.
Her 87.5k followers on Instagram are shocked by her death.
"So sad, she was not only gorgeous but also inspiring. I'm still in shock," wrote one fan on her last Instagram post.
"RIP Mandy! We all loved your spirit and energy," wrote another.