By Scott Malone

BLACKSTONE Mass. (Reuters) - A 31-year-old Massachusetts woman found living with the bodies of three dead infants in a rodent-infested house in a quiet suburb may be suffering from mental illness, her court-appointed lawyer said on Friday.

The woman, Erika Murray, did not speak during her brief appearance at Worcester District Course in Uxbridge, Massachusetts, where a not-guilty plea was entered on her behalf to a series of criminal charges.

Murray, handcuffed and dressed in a striped blue sweater, stared blankly as a judge ordered her held without bail pending trial. The charges include fetal death concealment, witness intimidation and animal cruelty.

Neighbors expressed shock near the beige, one-story home in Blackstone, Massachusetts, about 40 miles southwest of Boston, where police found the bodies of three young infants and the skeletal remains of several animals.

The house, where some windows were open on Friday and the front door was blocked with a cross of red hazard tape, held stacks of garbage and dirty diapers that in places were a foot deep, according to the Blackstone Police Department.

The ages and gender of the deceased infants found at the home have not been made public. Previously, four other children had been removed from the home and taken into state custody.

"Investigators can't go into that house without hazmat suits. She was living in that house. Who would be living in that house unless they were mentally ill?" her court-appointed attorney, Keith Halpern, told reporters.

Lisa McAdam, 52, said she passed Murray's house regularly on her daily walks through the town of 9,000 people on the border with Rhode Island and had never suspected anything amiss.

"When I heard what happened, what can you say? It's just awful that happened to little kids," said McAdam, who works at a nearby theater. "How can you just sit in that filth?"

The judge did not order the woman to undergo a mental health examination, but Halpern said that could take place privately.

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Police were first called to the house, a short walk from the town police department, last month after crying children were reported there. They found four children, ranging in age from three months to 13 years, who were taken into state custody.

Two of the children, aged 10 and 13, were determined to be Murray's, police said, but no birth records have been found for the two younger children.

Officials at the Massachusetts Department of Children and Families, which now has the surviving children in custody, did not respond to a request for comment on Friday.

A block from Murray's home, Sarah Martin, 29, was watering her neat garden as her two-year-old daughter picked flowers.

"It's not the sort of thing that anyone expects to happen," Martin said. She said she did not find the two-week gap between the state's first visit to the house and the discovery of the bodies terribly worrying.

"I imagine that they wanted to do all they could for the living children first," Martin said.

Murray could face up to 10 years in state prison if convicted of the most serious charge she faces, intimidation of a witness.

(Reporting by Scott Malone; Editing by Susan Heavey and James Dalgleish)