Colleen McCullough, whose novel "The Thorn Birds" sold 30 million copies around the world and was turned into a highly-rated 1983 television miniseries, died Thursday. She was 77.

HarperCollins Australia publishing director Shona Martyn told the Associated Press McCullough died in a hospital on remote Norfolk Island, almost 900 miles east of the Australian mainland. Martyn said McCullough had continued producing books despite a string of health and eyesight problems by using dictation.

"Ever quick-witted and direct, we looked forward to her visits from Norfolk Island and the arrival of each new manuscript delivered in hard copy in custom-made maroon manuscript boxes inscribed with her name," Martyn said in a statement. 

The cause of McCullough's death was not immediately released, but the Sydney Morning Herald reported that she had suffered a series of small strikes and was confined to a wheelchair. 

Before becoming an author, McCullough studied neuroscience and spent 10 years as a researcher at Yale Medical School. She established the neurophysiology department at Sydney's Royal North Shore Hospital.

She turned to writing late in life, composing 25 novels over the course of her career. Her first novel "Tim" was published in 1974, and her final book "Bittersweet" was released in 2013. "Tim" later became a movie starring Mel Gibson, who played a young, mentally disabled handyman who had a romance with a middle-aged woman.

But it was "The Thorn Birds," published in 1977, that secured McCullough's fame and fortune. The romantic saga of three generations of one family on a sheep station in the Australian outback became the highest-selling book from that country of all time. The paperback rights were sold at auction for a then-record $1.9 million. The ABC miniseries of the same name, which starred Richard Chamberlain, Barbara Stanwyck, and Christopher Plummer, became the second-highest rated miniseries in U.S. history, trailing only fellow ABC show "Roots."

McCullough is survived by her husband, Ric Robinson, whom she married in 1983. 

The Associated Press contributed to this report.