Japanese Kyodo News on Monday reported that over 50 students were hospitalised after a gas smell was detected at Kamei Elementary School in Yao.
According to the news source, around 09:00 a.m. local time (00:00 GMT), a gas smell was reported at an elementary school in Osaka prefecture.
As of 11:00 a.m., the smell was still present with a possibility of a gas leak not ruled out.
After the smell was detected, the children were evacuated to the schoolyard, where several dozen complained about feeling unwell which lead to the hospitalization of 51 children, Kyodo News said.
All the children were conscious and their health was not in danger.
The origin of the smell was investigated by local authorities, the report added.