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Erin Moran, the actress who played Joanie Cunningham on the hit TV series "Happy Days," has died in Indiana at the age of 56, police said.

TMZ first reported the death. The Harrison County, Indiana, sheriff's office told NBC News that dispatchers got a 911 call for an unresponsive female at 4:07 p.m. Saturday and first responders found Moran deceased.

Moran was just 13 when the show began in January of 1974. Viewers watched her mature on the show, which Moran said in a 2008 interview with the "Today" show wasn't the easiest passage to go through.

"It was so much fun with these guys," she said. "They made it better, they made it easier. I loved it. I had such a good time."

Moran played Joanie Cunningham, the younger sister of Richie Cunningham, who was played by Ron Howard. Her character was a love interest of the character Chachi, played by Scott Baio.

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The sitcom set in the 1950s in Milwaukee, which ran from 1974 to 1984, was a hit. Moran also co-starred along with Baio in the short-lived spinoff "Joanie Loves Chachi," which began in 1982.

Moran and Baio returned for the "Happy Days" final season, which ended with the two characters getting married.

Marion Ross, who played the Cunningham family mom on the series, remembered Moran as a smart, talented performer who easily adapted to the demands of filming and school.

"She would go to school, and she would come back after a break and would have to fit in to all the jokes we were doing on the set and pick up fast exactly where we were — which she could," Ross said in a telephone interview with NBC Los Angeles. "She was the quickest, fastest little kid. Wonderful."

"This breaks my heart," Ross said.

Henry Winkler, who played "The Fonz" in the series, expressed his condolences on Twitter, and said the death was too soon.

OH Erin... now you will finally have the peace you wanted so badly here on earth ...Rest In It serenely now.. too soon — Henry Winkler (@hwinkler4real) April 23, 2017

Howard said in a Tweet: "I'll always choose to remember you on our show making scenes better, getting laughs and lighting up tv screens."

Years after the show ended, Moran and three co-stars in 2011 sued CBS for $10 million over royalties they said they were owed, The Associated Press reported at the time.

The suit reportedly ended in an out-of court settlement in 2012 in which the four cast-members and the estate of another cast member received around $65,000 each.

Moran also made appearances in "Murder, She Wrote," and "The Love Boat."

An autopsy is pending and there is no indication of cause of death, the sheriff's office said.