DENVER -- Two people were advised in court Wednesday that they are under investigation in connection with the death of a 7-year-old boy, who Denver police said appeared to be malnourished.

The boy was found in a closet Sunday and weighed only about 30 pounds.

Denver police said the boy was taken to Swedish Medical Center from a southeast Denver home in the 3300 block of South Tamarac Street after receiving reports that the child was in cardiac arrest. He was pronounced dead Sunday afternoon.

Police said the child appeared to be suffering from malnutrition.

Detective John White of the Denver Police Department said Jon Phillips, 26, and 21-year-old Sarah Berry were being held for investigation of homicide. They were also advised in court Wednesday that they are under investigation of child abuse resulting in death.

It was not immediately clear how the boy and the suspects were related.

An autopsy was performed, but the cause and manner of the boy's death are pending further tests, Chief Deputy coroner Michelle Weiss-Samaras said.

Weiss-Samaras said the boy's name will be released once his family is notified and positive identification has been made.

Denver Human Services Manager Roxane White said the boy had a younger sibling whom the agency placed with a foster family.

"Our community is deeply saddened by the tragic death of a 7-year-old boy under highly suspicious circumstances on Sunday," she said. She said counterparts in Jefferson County also were investigating.

She wouldn't comment further, saying she did not want to compromise investigations by the police and prosecutors.

Neighbors say the couple kept to themselves, and that from the day they moved in, they put blankets over the windows, and kept strange hours.

"They were up at night, all the time," said a neighbor named Vahid, who only wanted to go by his first name.

His sister, Sousan, visits often, and says she noticed the boy and his younger brother were small, but didn't realize he was 7 years old.

"They were very short and tiny, very skinny," she said. "They seemed tired. That's the only thing I noticed, because usually kids are very welcoming. They say 'hi' or wave or say something, exchange words. They never did anything."

But other neighbors say they never saw anything alarming.

"They looked like normal, healthy boys, obeying their father," said Chrisandra Lundgren, who lives across the hall. "I did not hear them yelling or being disciplined in any way."