Scooby Doo
Scooby Doo and the rest of the gang Youtube/Screengrab

It has been revealed that actress Heather North died of a respiratory disease, which led to a heart attack and her subsequent death. She passed away at her Los Angeles home on 30 November, aged 71.

The death certificate obtained by TMZ list North's official cause of death as "cardiopulmonary arrest with an underlying cause of constrictive bronchiolitis".

North also had a very low level of oxygen in her blood when she died, the publication reported.

According to Hollywood Reporter, a memorial service for the actress was held on Wednesday (20 December) by the North Hollywood's First Christian Church.

Many of her fans were shocked to hear the news of her demise and took to social media sites to pay condolences.

"Aw, Jeepers. Such a great loss. We both attended the same church years ago. She was a beautiful & talented lady!" a Twitter user wrote, while another added, "Rest In Peace Heather North (71), the voice of Daphne. We lost an amazingly talented woman, with an iconic voice."

North was best known for voicing the character of Daphne Blake for over three decades on the original classic animated series, Scooby Doo, starting from 1970.

North played the role of Daphne from the second-season of Scooby Doo until 2003. She also reprised the character in The New Scooby Doo Movies in 1972-73. In the 2002 animated movie, Scooby Doo, Sarah Michelle Gellar reprised the role of Daphne Blake.

North appeared on TV shows like Mr Novak, Gidget, The Fugitive, The Monkees, My Three Sons and Adam-12. She also appeared on the big screen in Git! (1965) and I Love My Wife (1970).

North also starred as Kurt Russell's love interest in Disney's The Barefoot Executive (1971) and also played the role of Sandy Horton in the NBC daytime series, Days of Our Lives.

North met her husband H. Wesley Kenney on the sets of the television show. They got married in 1971.

Kenney passed away in January 2015. He was an Emmy Award-winning producer and director of soap operas. He was responsible for every episode of the show, All in the Family, between 1974 and 1975.