NEW DELHI (AP) — Indian athletes are urging London Olympic organizers to scrap a contract with the Dow Chemical Company over concerns about the firm’s links to a deadly toxic gas leak in India nearly three decades ago.

An estimated 15,000 people died when poisonous gas leaked from the Union Carbide factory in Bhopal in 1984. Dow Chemical bought Union Carbide in 2001 but denies responsibility for Carbide’s Bhopal liabilities.

Twenty-one athletes wrote to the 2012 Olympic organizing committee urging it to cancel Dow Chemical’s funding of a curtain-style wrap to encircle a London stadium where some Olympic events will be held.

Also on Monday, five Bhopal gas victims’ rights groups demanded the deal with the U.S.-based chemical company be scrapped.