An autopsy performed yesterday on a 2-year-old foster child who died Monday after being left in the care of a 12-year-old boy showed that the girl died of "blunt force injuries" to the head, stomach and back, D.C. police said.

D.C. Department of Human Services officials refused yesterday to discuss the death of Mykeeda Hampton or give details about the Northeast home where she and three other young foster children had been placed by the agency.

But they said in a statement that the foster children had been appropriately placed, that the home was licensed and that "there was no previous history of incidents of abuse or problems in the home." The other foster children were removed from the home immediately after Mykeeda's death, officials said.

Mykeeda was a foster child of Geraldine Stevenson of 2500 14th St. NE, according to police sources. An unidentified adult relative who went to the second-floor apartment shortly before 5 p.m. Monday saw the unconscious child and summoned an ambulance. Mykeeda was taken to Children's Hospital and pronounced dead about 10 minutes later.

Stevenson had left the 12-year-old boy to baby-sit for her four foster daughters all day Monday while she had her car repaired and then visited her boyfriend in Northeast, police sources said. Sources said the 95-pound boy told police he became frustrated and struck Mykeeda with his hands after she urinated on him.

In an interview on general agency guidelines for care of the District's estimated 2,300 foster children, Human Services spokesman Charles Seigel acknowledged that there are strict written rules that only baby sitters approved by the city may care for children while their foster parents are away from the home. But Seigel would not say whether the city certifies minor children as baby sitters.

No one has been charged in Mykeeda's death, but police sources described her as the victim of "a severe beating" who also had old bruises and scars on her body. Police and Human Services officials said last night that the investigation of Mykeeda's death was continuing.

Police said that Stevenson, who is in her forties, had been Mykeeda's foster mother for about a month. In May, she resigned her position as a procurement clerk with the U.S. Department of Interior's Bureau of Indian Affairs, where she had worked since 1971, apparently to devote herself full time to her foster parent responsibilities. The city pays foster parents $3,701 a year for each child younger than 12, and $3,862 for older children.

"D.C. is making an effort to make as many people as possible foster parents because we need foster parents," Seigel said.

In addition to the other foster children who had been in Stevenson's care -- 5-year-old twin girls and an 18-month-old girl -- three of Stevenson's four natural sons lived in the home, sources said.

The District's foster care system underwent public scrutiny after a March 1986 fire at the home of foster parent Frances P. Walker left five children -- four of them foster children -- dead. Also killed in the fire was Ellis R. Meeks, an unauthorized baby sitter who was caring for the children while Walker was out of town. An investigation revealed that Meeks was drunk when the fire broke out, had been convicted of manslaughter in 1972 and at the time of the fire was facing kidnaping and shooting charges.