London: Thousands of people around Bhopal remain at risk of poisoning by toxic waste contained in drinking water, 20 years after the gas tragedy which killed some 4000 people and left lakhs injured or disabled, a report claimed.

Four thousand people died after an explosion and toxic gas leak at a pesticide factory owned by US company Union Carbide in 1984, but thousands of tonnes of toxic waste are still stored inadequately nearby, poisoning the town's water supply, BBC said in an investigative report.

Union Carbide India Limited was responsible for cleaning up the site.

The BBC team in Bhopal took a sample of drinking water from a well near the site. "It had levels of contamination 500 times higher than the maximum limits recommended by the World Health Organization," the report claimed.

"The local people who drink this water every day are exposing themselves to a substantial chemical hazard associated, over time, with liver and kidney damage," it added.

According to the report, the Union Carbide disputed the test results saying, when it handed the site back in 1998 it "found no evidence of groundwater contamination".

When the company was presented with details of the chemicals they had found, it said it was "not aware of any evidence to support such claims", according to the report.

But there are still thousands of tons of toxic waste on the abandoned and dilapidated site, lying in piles exposed to the weather, the BBC claimed.