Tochigi Prefecture Police have arrested the former owner of a child care facility in Utsunomiya and her two children for causing the death of a 9-month-old girl who was under their care last year.

The police on Thursday arrested Yokohama resident Kumiko Kimura, 58, as well as her daughter Remi, 28, and her son Taka, 23, who both worked at the Toys child care facility, on suspicion of neglect resulting in death.

None has admitted guilt in the infant's death in July 2014, police said.

The trio allegedly did not inform the parents of Emiri Yamaguchi that their child had developed diarrhea and a fever above 38 degrees Celsius during her stay at the unregistered facility between July 23 and 26 last year. The police say the Kimuras failed to send her to a doctor and ignored the child's condition. The girl died in the early hours of July 26 from heatstroke.

Police said that at the time of the incident, Emiri was the only child at the facility. They said they were investigating the trio's actions before and after the girl's death, as well as the facility's operations.

The police are also scrutinizing several images given to Emiri's parents by a person claiming to be a former worker at the facility. The photographs, presumed to have been taken inside the facility, reportedly show children tied up.

"We're glad to hear (the Kimuras) have been given an arrest warrant before the first anniversary of the death of our daughter," Emiri's parents said at a news conference at the Tochigi Prefectural Government office.

In May 2014, police received an anonymous tip about another child being physically abused at the same facility and conducted an on-site inspection, but failed to find any evidence.