Updated

Four small, malnourished boys taken from a Denver apartment because of uninhabitable conditions faced abuse and could only communicate in grunts, according to an arrest affidavit that described a disturbing scene of feces, urine and flies at the residence.

The document released Monday said Denver police found the children - ages 2, 4, 5 and 6 - living in a residence with an "unbearable" smell of a decomposing animal. They were not toilet trained and had no schooling of any kind, according to the affidavit.

All four boys have been placed in protective care and have undergone hospital exams that found them to be non-verbal, malnourished and not toilet trained.

Their parents - Wayne Sperling , 66, and Lorinda Bailey, 35 - are being charged with four counts of felony child abuse and are due to appear in court Tuesday. The couple pleaded guilty in June 2009 to misdemeanor child abuse, according to the affidavit first obtained by KMGH-TV.

The current charges against the parents come after an investigation that began Sept. 29 when Bailey took her youngest son to St. Joseph's Children's Hospital for a cut on his forehead that she said happened after a fall, the news station reported. An emergency room doctor informed authorities that the child was unwashed and smelled like cigarette smoke, prompting a welfare check by a Denver Human Services case worker. Bruising behind the child's right ear appeared consistent with pinching, the doctor said.

Denver police Officer N. Rocco-McKeel accompanied the case worker to the apartment at her request and reported finding five cats and feces on the floor throughout the apartment. The source of the foul odor reported by authorities could not be located during the visit but seemed to be coming from a room where flies covered "every surface."

The mother said she did not think the apartment was unsafe and denied the boys had any developmental delays. Rocco-McKeel said the three oldest children appeared similar in size, KMGH-TV reported. The mother said she had been living alone in a separate unit of the building for the past two months, but still saw the children almost every day.

Sperling, meanwhile, told investigators he was unemployed and has been the boys' primary guardian. He intended to begin home-schooling the 6-year-old.

He also said the feces on the floor of the apartment was that of the cats'. The affidavit said there was 1-2 inches of cat feces under the bunk bed where the boys slept and the floor was soaked with cat urine.

KMGH-TV also reported a doctor with the Family Crisis Center told police that it did not appear that the children regularly visited the doctor and the 5-year-old had no records whatsoever.