The parents of Nathalyz Rivera were arrested on suspicion of homicide and child abuse after the three-year-old, who had been born blind and with Down syndrome, was brought to Philadelphia's Einstein Medical Center and pronounced dead. She weighed eleven pounds, and her body was covered in festering wounds that doctors believe to be insect and rodent bites.

"This is one of the worst cases of abuse that I've seen in my five years on the homicide unit. Very sad and very disturbing," Philadelphia Police Homicide Captain James Clark said during a press conference Monday afternoon.

According to Captain Clark, 30-year-old Carlos Rivera returned home around midnight on Monday and found that the girl was not breathing. Instead of calling 911, he phoned the girl's mother, 27-year-old Carmen Rameriz, who had been staying at a boyfriend's house. The mother and her boyfriend took the girl to Einstein Medical Center, where doctors pronounced her dead at 1:50 a.m.

A child-abuse pediatrician with Children's Hospital of Philadelphia familiar with the case, Cindy Christian, told the Philadelphia Inquirer that the girl's condition "doesn't happen to a child in a couple of weeks. Generally, it is a process that takes months and months, or even years of neglect."

She had "starved like people in concentration camps starved," Christian said.

The house she lived in was flea-infested, and the floor was littered with rat droppings. Crime-scene investigators wearing protective hazmat suits searched the home where the child was found. The family had moved in four years ago, and the house was in a state of perpetual disrepair. Nathalyz's siblings -- including a twin brother -- are now in the care of the Department of Human Services.

In a statement, Alicia Taylor, a DHS spokeswoman, said "[w]e are working with police. Our job is to make sure that the other children in this family are safe, and that includes that they are checked out of the hospital and cleared medically." Neighbors told Philadelphia's ABC affiliate that the other children were "[d]irty, very thin, pretty kids, very pretty."

Watch the ABC 6 News report on the incident here: