An abnormally high level of dioxin has been detected in the blood of residents living near a controversial garbage incineration plant in Ibaraki Prefecture, researchers announced Thursday.

A team headed by Professor Hideaki Miyata of Setsunan University's pharmaceutical department said the body fat of residents near the plant in Shin Tone had a maximum 463 picograms of dioxin per gram. The level is extremely high when compared with the norm, the team said. One picogram is one-trillionth of a gram.

Dioxin is a highly toxic substance that causes cancer and deformities. The level of dioxin ranges from several picograms to about 30 picograms in residents living near an incineration facility in Saitama Prefecture and in Vietnamese residing in areas contaminated with Agent Orange, a defoliant used by the United States.

The findings are expected to affect the outcome of a lawsuit in which local residents are demanding a halt to the operation of the Shin Tone plant.

Miyata's team reported its findings at a symposium on environmental chemistry held in Kyoto. The team drew blood from 53 residents living near the incineration plant in March 1996. So far, it has determined the levels of dioxin in 18 of the residents -- five women and 13 men.

The five women had an average 149 picograms and the 13 men an average of 81 picograms per 1 gram of body fat in terms of the most toxic type of dioxin. The highest level detected was 463 picograms and the lowest 22 picograms.

The Shin Tone incineration plant started up in 1971, burning garbage from municipalities in and around Ryugasaki, Ibaraki Prefecture.