JACKSONVILLE, Fla. -

Police have made a second arrest in a case of aggravated child abuse of a 1-year-old girl brought to Wolfson Children's Hospital on Friday night.

Yuri Mito, 20, was arrested Monday on a charge of failing to seek prompt medical treatment for the girl.

Police said the girl appeared to have a rib fracture, internal bleeding, and external bruises on her stomach and back. The girl underwent surgery and remained at the hospital in stable condition. She was expected to make a full recovery.

Tommy Butler, 28, was charged on Friday night with aggravated child abuse causing great bodily harm, permanent disability or disfigurement.

"These children are incredibly fragile and something like this could have been much worse," said John Harrell of the Division of Children and Families earlier this week.

Detectives have continued to investigate injuries to the girl that caused doctors to notify child protection authorities. Police have not released her relationship to the child and the mother's name was redacted from the original incident report.

The mother took the girl to the hospital Friday night and told police her daughter started getting sick and throwing up on Thursday, so she took her to the hospital. She said she didn't know where the girl's bruises came from and said they may have happened while at the girl's father's house, according to a police report.

According to police report, the mother of the 1-year-old told investigators the girl had spent the previous weekend away from home with other relatives.

DCF believes Butler is the boyfriend of the girl's mother.

"Something that concerns us, in addition to the abuse, is that this man is the boyfriend of the mother of this child. And the stats show that 67 percent of child abuse cases nationally involve a perpetrator who is the boyfriend of the mother of the child," said Harrell.

Mito has been released on $20,000 bail. Butler remained jailed Thursday on $100,000 bail, according to jail records.