A 3-year-old girl died Monday after she was likely left for about five hours inside a kindergarten school bus in Makinohara, Shizuoka Prefecture, police said.

China Kawamoto is suspected of dying of heatstroke, according to the Shizuoka city fire department, which has jurisdiction over Makinohara.

On Tuesday, police searched Kawasaki Kindergarten and the home of its director and principal, Tatsuyoshi Masuda, 73, in Makinohara on suspicions of professional negligence resulting in death in connection with the case.

"I can't say anything now as police are investigating. I'm sorry," Masuda said in front his house Tuesday morning.

The bus arrived at the kindergarten at around 8:50 a.m. Monday and school staff found Kawamoto unconscious inside the bus at around 2:10 p.m. the same day, according to police. She was subsequently confirmed dead.

Five other children and a staff member in her 70s had also boarded the vehicle with Masuda in the driver's seat. Masuda drove the bus on Monday as the kindergarten's bus driver was taking a day-off.

When a staff member boarded the bus shortly after 2 p.m. to send kindergarteners home, Kawamoto was found inside. The girl's body temperature was high at the time she was transported to a hospital, according to the fire department.

According to police, the kindergarten said staff locked the bus after arriving at the kindergarten, but did not thoroughly check inside the bus when disembarking children.

The incident came after a 5-year-old boy died of heatstroke in Nakama, Fukuoka Prefecture, in July 2021 after being left in a locked nursery school bus for about nine hours. The Fukuoka case prompted the welfare ministry to send a notice to local municipalities to ensure proper measures are taken to prevent similar incidents.

A high of 30.5 degrees Celsius was observed in Makinohara at around 12:55 p.m. Monday.