A concentration of trichloroethylene 1,600 times above the national environmental standard has been detected at the site of a former Nissan Motors Co. plant in Tokyo's Suginami Ward, company officials said Friday.

According to Nissan officials, trichloroethylene -- which is believed to cause cancer in humans -- was found to exceed the national standard of 0.03 mg per liter at 11 points within the 90,000-sq.-meter plot in Suginami's Ogikubo district during a recent inspection.

At one point, a concentration of 49 mg per liter was detected, according to Nissan.

The inspection also showed that groundwater at the site has been contaminated by the substance at levels up to 11 mg per liter.

The officials said, however, that the finding does not pose an immediate health hazard to people living in the area.

The Ogikubo plant was the development and production base for Nissan's aerospace division between 1966 and March 1999, when it closed.

The material has until recently been widely used as a cleaning solvent and the company had used it for 25 years until switching to an alternative in 1989, the officials said.

Contamination appears to have been caused when the toxic chemical leaked from cracked drainpipes, they said.

In Nissan's inspection, cadmium was found in concentrations up to 6.5 times the national standard in soil at the site's former dumping grounds.

The inspection was carried out following the decision to sell the plot as part of the auto manufacturer's restructuring efforts.

However, Nissan officials revealed at Friday's news conference that in a similar inspection conducted in 1994, they detected up to 15,000 times the national standard of trichloroethylene at the site but decided not to make the findings public.

The company will begin a clean-up operation next month that is likely to last six months and cost several billion yen, the officials said.