US actress Erin Moran, who played mischievous kid sister Joanie on the sitcom "Happy Days" and its spin-off "Joanie Loves Chachi," has died.

She was 56.

The Harrison County Sheriff's department in Indiana said Moran was found "unresponsive" following a 911 call to the authorities at 4:07 pm (2007 GMT) on Saturday.

"Upon the arrival of first responders, it was determined that Erin Marie Moran Fleischmann was deceased and an autopsy is pending," it said.

A sheriff's department spokeswoman told AFP it was unclear when the autopsy would take place but cautioned it would likely take some time because her death occurred in a small town. The cause of death was undetermined.

In the series "Happy Days," which had a 10-year run from 1974 to 1984, Moran was cast as Joanie Cunningham, sister to older brother Richie, played by Ron Howard.

Howard and other former co-stars shared their condolences via social media.

"Such sad sad news. RIP Erin. I'll always choose to remember you on our show making scenes better, getting laughs and lighting up TV screens," Howard tweeted.

Henry Winkler played Arthur "Fonzie" Fonzarelli. a character who lived in an apartment over the Cunninghams' garage.

"OH Erin... now you will finally have the peace you wanted so badly here on earth ...Rest In It serenely now.. too soon," he wrote.

Moran was believed to have fallen on hard times in recent years as she struggled to secure other acting gigs.

The Indianapolis Patch news website reported that Moran was found unresponsive in a trailer park in the small town of Corydon.

"I've known Erin Moran since childhood doing 'GunSmoke.' More recently as a troubled soul. So saddened to hear of her passing. RIP ERIN xo," wrote Willie Ames, who appeared alongside Moran when they were children on the series "Gunsmoke."

source: AFP