Pulitzer Prize winning author, Nelle Harper Lee, has died at the age of 89, according to family members.

Lee was best known for her novel To Kill a Mockingbird, which helped give context to racial injustices in the American deep south. The book was published in 1960 and won a Pulitzer Prize for fiction the following year.

To date the novel has sold over 40 million copies worldwide, according to publisher HarperCollins.

The film adaption of To Kill a Mocking Bird was released in 1962 and starred Gregory Peck and Mary Badham. It is currently ranked by the American Film Institute as one of the best films ever made.

Lee's Go Set a Watchman, a widely accepted first draft of the 1960 novel, was published in 2015.

"Knowing Nelle these past few years has been not just an utter delight but an extraordinary privilege," said Andrew Nurnberg, Lee's literary agent, in a statement. "When I saw her just six weeks ago, she was full of life, her mind and mischievous wit as sharp as ever. She was quoting Thomas More and setting me straight on Tudor history. We have lost a great writer, a great friend and a beacon of integrity.”

Services for Lee have not yet been announced.