Four days after a deadly gas leak at Union Carbide's plant in Bhopal killed thousands in 1984, the company's chairman, Warren Anderson, was arrested on his arrival in the capital of Madhya Pradesh. But after being held under house arrest for only a few hours, Anderson posted bail and quickly left the country, never returning to face trial.

Several reports have suggested that the government of PM Rajiv Gandhi was pressured by the US to let Anderson go. Senior Congress leader Arjun Singh, who was then the chief minister of MP, wrote in his autobiography A Grain of Sand in the Hourglass of Time that home secretary R.D. Pradhan called him "on the instructions of the then Union home minister P.V. Narasimha Rao".

Pradhan denied the allegation, saying he was chief secretary of Maharashtra at the time and became Union home secretary only in January 1985. Singh died in 2011 after a prolonged illness. Moti Singh, who was the Bhopal collector at the time of the disaster, said Anderson managed to get away by using a phone in the room where he was detained to contact persons in the US.

"Had we removed the landline phone from his room, Anderson would not have escaped. He possibly made calls to contacts in the US to help him leave India," Singh added. The US embassy reportedly mounted pressure on the Indian government, which released Anderson on a personal bond of ` 25,000.

Anderson never returned to face trial and was declared a fugitive by Indian courts. Rights activists have blamed successive governments for failing to secure the extradition of the man who was held responsible for the death of around 15,000 people. Over half a million people were injured by the gas, and many of them died slowly from illnesses like lung cancer, kidney failure and liver disease.

Anderson was arrested after the CBI took over the investigation on December 6, 1984. While he was being held at the Union Carbide guest house, he spoke to Indian officials and legal advisers of the company. The six-foot-two-inch tall executive, then aged 63, wanted to visit the factory but was discouraged by the local administration.

Swaraj Puri, Bhopal's Superintendent of Police in 1984, claimed Anderson was arrested on a written order and released on an oral order. "We arrested him on the basis of a written order but released him on an oral order," Puri told the Union Carbide Toxic Gas Leakage Enquiry Commission. He added that the oral order came "from higher-ups".