LAKE STEVENS — Three children have been taken into protective custody after police found them apparently abandoned by their parents and living in filthy conditions, detectives said Tuesday.

The parents were arrested Tuesday at a Child Protective Services hearing and booked into the Snohomish County Jail, Lake Stevens police detective Dean Thomas said.

The man and woman, both 32, were being held Tuesday for investigation of felony mistreatment and abandonment of dependents.

A 7-year-old girl, 3-year-old boy and their 10-month-old brother likely had been alone in the house for days. The baby was alone in a locked room, wearing a heavily soiled diaper. He was hypothermic and dehydrated. The older children had no food and cowered under filthy blankets when police officers knocked on the door.

There was so much human and animal waste inside that officers wore respirators and plastic boots.

Police were called to the house along 11th Place SE on Saturday. A woman had gone there because she was owed money by one of the suspects, documents show.

She called authorities to report possible child neglect.

“Patrol (officers) could hear little footsteps coming to the door and little footsteps walking away from the door,” Thomas said.

They persuaded the oldest child, the 7-year-old girl, to let them inside, Thomas said.

She told them her parents were upstairs with her baby brother. In truth, there were no adults in the home.

The 3-year-old boy was underneath filthy blankets and laundry on a couch. The baby upstairs wasn’t moving and was unresponsive to voices, Thomas said. A space heater had been left on in the room near a pile of dirty diapers.

All three children were taken to Providence Regional Medical Center Everett for treatment. An update on their condition was not available Tuesday afternoon.

Nurses told Thomas that medics at the house had measured the baby’s temperature at 94.1 degrees — hypothermic. He also was dehydrated, he said. All three children are expected to survive.

Inside the house, holes were knocked in exterior walls and daylight could be seen, documents show. The building originally was a duplex but there were holes in the drywall between the two units.

“There was no heat. It was 40 something degrees in the house,” Cmdr. Dennis Taylor said.

Detectives served a search warrant at the house on Tuesday to collect evidence. The house also was ordered condemned and unsafe for habitation, said Chad Osterholtz, the city code inspector.

The house had running water and power but there also was extensive water damage and mold. The floor was covered in feces and urine, according to police. The smoke alarms were disabled, wires were exposed and light fixtures uncovered.

“It was just disgusting,” Osterholtz said.

Raw sewage was spilling from a camper parked outside. One of the children’s grandmothers was living in the camper, according to public records. Another grandmother owns the house. Neither woman cooperated with police.

The family has a history of contact with CPS, Thomas said. The 7-year-old’s school recently had called social workers after the girl missed a week of school, he said. The girl had extensive absences, and the school previously had talked to CPS about concerns regarding her health and appearance, Taylor said. It is unclear when those reports were made to social workers.

The Herald is not yet naming the parents because they have not been charged with a crime. They are due to make a first court appearance Wednesday in connection with the allegations that led to their arrests.

Both suspects are convicted felons. The man was sentenced in 2002 to eight years in prison for a shooting in Arlington. He shot a man in the arm and buttocks during a confrontation. He had already racked up six felony convictions as a juvenile.

The woman graduated from drug court in 2009. Three years later she was convicted of stealing a Ford Explorer.

Thomas, who has been with the police department for nine years, called the conditions of the house “horrific.”

“It’s the worst house I’d ever been in with children living in it, by far the worst,” he said.

The older children appeared to be living in a back room, with crayon scrawled on the walls around them, Osterholtz said. They appeared to be sharing a couch and cushions for sleeping and did not have beds.

“You could just tell those kids raised themselves in there,” Osterholtz said. “It’s the worst thing I’ve ever seen.”

Rikki King: 425-339-3449; rking@heraldnet.com.