A 71-year-old woman found dead in her home is determined to have been killed by a black bear, in the first known fatal attack by one of the animals in California.

When police entered Patrice Miller’s home in November to conduct a welfare check, they initially thought the bear had found her after she died.

However, a recent autopsy report confirmed that it was the bear that killed Miller.

“The coroner’s report confirmed that, ultimately, the bear caused the woman’s death,” the California Department of Fish and Wildlife said.

Police from the Sierra County Sheriff’s office said the bear was not in Miller’s home when they discovered her body on 8 November.

A preliminary investigation had earlier determined that the woman died before the bear’s entry.

The bear, a male, was later trapped and euthanised – after which DNA testing confirmed that it was responsible.

Following the autopsy report, Sierra County Sheriff Mike Fisher told local media that Miller was killed when the bear swiped or bit her neck.

Bear attacks on humans are uncommon, state wildlife officials said. However, the animals “lose their natural fear of people and their actions get bolder and bolder” when homes and campgrounds are viewed as easy food sources.

“This is the most extreme example we’ve seen in state history,” Peter Tira, a spokesperson for the California Department of Fish and Wildlife, told the Los Angeles Times.

Authorities said Ms Miller, who lived in the small mountain community of Downieville, had multiple issues with bears on her property. She is said to have often fed her cats on the porch and had trash on the property.

The woman had physically hit one bear to stop it entering her residence, her daughter was quoted as saying by the LA Times.

There are up to 35,000 black bears in California, according to the state wildlife department.

Adult males can weigh roughly 400lb (181kg). Females range from 100-300lb.