An Iraqi woman who was found severely beaten at her San Diego home next to a note saying "go back to your country" has died.

Shaima Alawadi, 32, a mother of five, was found unconscious by her 17-year-old daughter on Wednesday, police said.

The daughter, Fatima al-Himidi, told local TV that her mother had been beaten on the head repeatedly and that the note said: "Go back to your country, you terrorist."

Hanif Mohebi, director of the San Diego chapter of the Council on American-Islamic Relations, said he met Alawadi's family members on Saturday morning and was told later she had been taken off life support.

"The family is in shock at the moment. They're still trying to deal with what happened," Mohebi said.

Police said the family had found a similar note earlier this month but had not reported it to authorities. Himidi said her mother had dismissed the first note as a child's prank.

A family friend, Sura Alzaidy, told the San Diego Union-Tribune that the attack apparently occurred after the father took the younger children to school. Alzaidy said the family is from Iraq and Alawadi was a "respectful modest muhajiba", meaning she wore the hijab.

Investigators said they believed the assault was an isolated incident. "A hate crime is one of the possibilities, and we will be looking at that," Lieutenant Mark Coit said. "We don't want to focus on only one issue and miss something else."

The family had lived in the house in San Diego County for a few weeks, after moving from Michigan, Alzaidy said. She told the newspaper that her father and Alawadi's husband had previously worked together in San Diego as private contractors for the US army, serving as cultural advisers to train soldiers going to the Middle East.

Mohebi said the family had been in the US since the mid-1990s. He said it was unfortunate that the family had not reported the initial threatening note.

"Our community does face a lot of discriminatory, hate incidents and don't always report them," Mohebi said. "They should take these threats seriously and definitely call local law enforcement."

El Cajon, north-east of central San Diego, is home to 40,000 Iraqi immigrants, the second largest such community in the US after Detroit.