Erin Moran, the former child actor who played the sweet but mischievous Joanie on the television series “Happy Days” and “Joanie Loves Chachi,” has died. She was 56.

The Harrison County Sheriff’s Department in southern Indiana confirmed her death. Ms. Moran was found unresponsive Saturday afternoon and died in her home in New Salisbury, Ind., the authorities said.

An autopsy showed that she most likely died from complications of cancer, the sheriff’s department said in a statement on Monday.

Ms. Moran, who started acting at 5, got her first taste of television in a commercial for First Federal Bank. She went on to play minor characters on television and in film in the late 1960s and early ’70s. At 12, she landed her biggest role: Joanie, the freckle-faced troublemaker and sister of Richie Cunningham, the all-American teenager played by Ron Howard.