Officials in France start investigation after twenty victims of Saddam Hussein’s 1988 chemical weapons attack on the Kurdish town of Halabja filed a complaint in Paris on June 11 in a bid to shine a light on companies that helped the former Iraqi regime to build a chemical arsenal.

The March 1988 attacks in Halabja remains the deadliest chemical weapons attack against civilians in history. Saddam ordered the poison gas strikes to crush the rebellion of Kurdish Peshmarga fighters.

Four of the victims made the trip to France, two of whom have suffered from severe respiratory problems since the bombing, which killed some 5,000 Kurds.

Two French companies, whom have not yet been named, were among the 20 or more companies that helped Saddam construct a chemical weapons arsenal.

According to lawyer David Père, the French companies that have been targeted made equipment for producing chemical agents and reactors, as well as columns and steel tanks used to contain the toxic agents employed in manufacturing the gas.