Mandatory devices that prevent children from being left inside buses will be installed in just about 55 percent of the vehicles used by preschool institutions across Japan by the end of June, a government survey showed Tuesday. According to the survey results released by the Children and Families Agency, as of May 15, the devices had been installed in only 16 percent of the vehicles. The Japanese government ordered preschools to install safety devices in about 50,000 buses, starting in April this year. The move came after a fatal incident occurred last September in Shizuoka Prefecture where a three-year-old girl died from heatstroke after she was left behind in a preschool bus. While setting a one-year transition period for installing such devices, the government had urged the operators of preschools to do this by the end of June, as the risk of heatstroke rises in the summer. "Considering the fact that we have called for safety devices to be installed by the end of June as many as possible, we can't say that it's enough," Masanobu Ogura, minister in charge of policies for children, said at a press conference. Ogura added that his agency is going to analyze the situation and urge the operators to install the devices as soon as possible.