An Arizona couple was formally charged Wednesday with the death of their 3-year-old daughter whom authorities say weighed just 15 pounds and had numerous injuries when she died last weekend.

Carlos Cruz, 28, and Rosemary Velazco, 36, are accused of first-degree murder and felony child abuse, according to the Maricopa County attorney’s office. The Surprise couple had previously been jailed only on suspicion of one count of child abuse.

Surprise police said the child showed signs of being beaten and being sexually abused when she was taken to the hospital and pronounced dead Saturday. The child was set to turn four years old a week later.

In a jailhouse interview with KTVK, Cruz denied he abused his daughter in any form.

"I'm not guilty of what they're investigating," Cruz told the Phoenix TV station. "My conscience is clean. ... She's my blood. She's my daughter."

Police say the girl showed signs of extreme malnourishment, had injuries all over her body that were in various stages of healing and had a 1-inch cut on her forehead that exposed her skull.

Investigators said Velazco told them her husband has anger issues and would use a belt to repeatedly whip the girl and her 6-year-old brother.

"Yes, I would hit her. I can't say I didn't," Cruz told KTVK. "I would hit her but not to the point of killing her. Two on the behind or one with a belt. The normal."

Serving a search warrant, police found a small paint can that appeared to be used as a toilet by the children, and the girl’s bed, which was a 2-foot-by-2-foot wobbly wooden structure. The siblings shared a bedroom with their parents.

Police also said there was little food in the refrigerator, but the freezer contained beer.

"I was told by investigators this is one of the worst cases of child abuse and neglect they have seen in their career," Surprise police Lt. Bert Anzini said.

Arizona Department of Child Safety officials said the girl was removed from the home in 2011 when she and her mother tested positive for amphetamines at her birth.

Cruz and Velazco remain jailed on bail of $500,000 apiece.

The couple's 6-year-old son and an infant are in foster care, according to authorities. Cruz said he hopes he can put the allegations behind him and regain custody of the two children.

The Associated Press contributed to this report.