A group of citizens and scientists claimed Friday that Japan’s science ministry may have manipulated measurements of radiation levels in Fukushima prefecture, Asahi Shimbun reports.

A survey conducted by the Association for Citizens and Scientists Concerned About Internal Radiation Exposures this year indicated that airborne dose levels in 100 monitoring posts set up by the Ministry of Education, Culture, Sports, Science and Technology were 10-30% higher than the ministry’s figures. The discrepancy was even greater in some areas – about 10 meters away from the posts, the readings averaged 40-50% higher.

“We are afraid that the ministry might have thoroughly decontaminated areas immediately adjacent to the monitoring posts or tinkered with numbers in an attempt to get lower readings,” Katsuma Yagasaki, a professor at the University of Ryukyus, which is in Okinawa, told a news conference. An official from the ministry’s nuclear disaster response section denied such accusations, saying, “We have never intended to show radiation lower than actual levels”.

This comes after the health ministry claimed that levels of radioactive contamination found in food items are declining. According to a survey by Asahi Shimbun, only 1% of food samples in Fukushima are contaminated.