June Foray, the voice behind popular cartoon characters including Rocky the Flying Squirrel from The Rocky and Bullwinkle Show and How the Grinch Stole Christmas' Cindy Lou Who, died Thursday at age 99.

Friend Dave Nimitz, an animator, confirmed Foray's death on Facebook, writing that "we lost our little June today at 99 years old." The cause of her death has not yet been announced.

In addition to Rocky and Cindy Lou, Foray was also the voice of a number of iconic animated characters, including Rocky and Bullwinkle nemesis Natasha Fatale, Dudley Do-Right's Nell, Granny of Tweety and Sylvester fame, and Witch Hazel from Looney Tunes. Her IMDB page lists more than 300 credits, including appearances in more recent projects like Mulan, Family Guy, and The Powerpuff Girls.

Foray additionally voiced characters in dozens of other classic films and shows, such as The Flintstones, The Twilight Zone, Peter Pan, Cinderella, Who Framed Roger Rabbit, and Space Jam.

Referred to as "The First Lady of Cartoon Voices," Foray helped establish the animation industry's Annie Awards, and later lobbied for the creation of an animated feature category at the Academy Awards. As Variety reports, Foray was also among the original membership of the International Animated Film Association (ASIFA), a non-profit benefitting animated film creators started in 1960 in France.

Foray's work earned her a Hollywood Walk of Fame star in 2000. She later took home her first Emmy, a Daytime Emmy for Outstanding Performer on an Animated Program for her work on The Garfield Show, in 2012. A Primetime Emmy came in 2013, with Foray taking home that year's Governor's Award, which recognizes individuals for outstanding achievement across their careers. Her first major award, however, was a 1968 Grammy for her work on How the Grinch Stole Christmas.

A documentary about Foray's life, The One and Only June Foray, was released in 2013.

ASIFA-Hollywood president Jerry Beck issued a statement following Foray's death calling the voice actor a "trailblazer, a great talent, and a truly wonderful person."

"We will never forget her," Beck added.