The skeletal remains of 3-year-old boy were found in a toy chest inside a structure on the property of a house on the city's south side, Tucson police said Wednesday.

Police Chief Roberto Villaseñor said the remains, found Tuesday by a landlord cleaning the property, have been tentatively identified as Roman Barreras.

Villasenor said the toddler's mother, Raquel Barreras, 39, was arrested and is facing charges of first-degree murder and child abuse. The boy's father, Martin Barreras, 45, is facing charges of child abuse.

The family, which included four other children, had been evicted earlier this year from the rental house, which is a triplex. He said three other children who are minors have been turned over to the state's child protective services agency. A fourth child is 19 and was not placed in protective custody, he said.

The younger children are a 12-year-old son, a 7-year-old daughter and a 4-year-old daughter, the chief said.

A landlord cleaning the home in the 700 block of West Idaho Street found the skeletal remains in a blue toy box and called 911, said Sgt. Chris Widmer, a Tucson Police Department spokesman.

When officers arrived, they confirmed the bones were those of a young child, Widmer said.

The report came in about 3 p.m. that the remains were found outside the house on the property, Widmer said. The neighborhood is west of South 12th Avenue, north of West Nebraska Street.

Villaseñor said the boy was apparently forced to live for periods of time in the attached structure that was in the yard of the house. He said police officers had been to the house before, primarily for reports about the older children not attending school.

He said the family had previous contact with state child welfare workers. That agency, he said, had taken the children away on previous occasions but returned them to the parents, he said.

He said when officers went to the home previously there were no outward signs of the children being abused. He said the children taken into protective custody appear to be in good health.

After discovering the remains Tuesday, police contacted the family later that evening, he said. They were at another home near the Tucson Rodeo Grounds.

An official with the Division of Child Safety and Family Services, the former CPS, confirmed caseworkers had contact with the family. However, the last contact was in August 2012. More information was not immiediately available.

A family member contacted by the Star declined comment Wednesday. Relatives of the family are expected to speak at a news conference on Thursday morning.