Traces of radioactive cesium have been discovered in schoolchildren in Fukushima Prefecture, according to the Minami-Soma municipal general hospital.

Half of the elementary and junior high school students in Minami-Soma who underwent radiation checks since late September were found with low levels of radioactive cesium-137, the hospital reported.

"We will offer periodic checks to students to keep records of their health conditions," said a hospital worker in charge.

The hospital is uncertain whether the students inhaled airborne radiation or ingested it through radiation-contaminated foodstuffs after the March 11 Fukushima No. 1 nuclear power plant accident.

Radioactive cesium-137 was detected at below 10 becquerels per kilogram of a student’s weight in 199 students. The substance was also found at from 10 to less than 20 becquerels in 65 students; 20 to less than 30 becquerels in three students; and 30 to below 35 becquerels in one student, the hospital said.