The 33-year-old former owner of a nursery school in Morioka, Iwate Prefecture, was arrested Tuesday on suspicion of inflicting injury resulting in death after she gave a drink containing salt to a 1-year-old girl, causing her to die from sodium poisoning.

According to the Iwate Prefectural Police, Naoko Yoshida is suspected of giving Ako Shitasaka, who was being cared for at the facility, a drink containing salt sometime between 10:30 a.m. on Aug. 17, 2015, and 12:05 a.m. the following day.

Yoshida admitted to giving the drink to the child but denies that she intended to cause harm, according to the police. At the time of the incident, Yoshida and Shitasaka were the only ones at the facility.

The child got sick after her father, Wataru Shitasaka, 27, picked her up on Aug. 18. She was taken to a hospital but died five hours later.

According to the Morioka Municipal Government, the facility opened in July 2015 and shut down a month later after the girl's death. The police are investigating Yoshida's motive.

A sudden massive intake of salt can make people feel thirsty and vomit, according to Dr. Yoshito Izutani of Okinawa Miyako Hospital in Okinawa Prefecture, who is knowledgeable about sodium poisoning. The sodium can get into the bloodstream and travel to the brain, damaging its functions. In the most severe cases it makes people unconscious and can lead to death.

"Our beloved Ako died on the day of her 1st birthday," her parents said in a statement upon Yoshida's arrest. "We have gone through an inexplicable degree of outrage and suffering, in addition to the sadness of losing her. We hope the truth will be revealed to prevent similar incidents from ever happening again."