Dozens of tons of banned chemicals were exported by three Antwerp-based companies to Syria and Lebanon after July 2013, in violation of an export ban that had been in force since 2014, Belgium’s Finance Minister Johan Van Overtveldt said after he confirmed a report by the Belgian media on April 17.

The three Belgian companies have been accused of exporting chemicals to Syria, including isopropanol, a common substance that can also be used in the production of sarin nerve gas. Sarin is a type of nerve gas developed by Germany prior to World War II as a pesticide. It is classified as a nerve agent due to its poisonous effects on the central and peripheral nervous systems.

Sarin is believed to have been the nerve agent used in the most recent chemical attack by the Bashar al-Assad regime in Syria.

The export of chemicals to Syria has been subject to special authorisation since 2013, but Belgian customs apparently did not take into account the ban of the International Organization for the Prohibition of Chemical Weapons of the United Nations.

The trial, which will start in Antwerp on May 15, centres on the export of several chemical substances between 2014 and 2016. The case against the three Belgian firms – AAE Chemie, Danmar Logistics, and intermediary Anex Customs – was first reported by the Belgian news site Knack following an investigation in collaboration with the Syrian Archive group.

“The companies had no export licence for these products,” a spokesman for the court said.

“Both of my companies and AAE Chemie have always acted in good faith. We have always fully complied with the checks of customs officers at the port of Antwerp,” a spokesman for Danmar Logistics said. Under Belgian law, a defendant is not required to enter a plea.

The firms say they acted with the consent of Belgian customs officials between 2014 and 2016 but were subsequently alleged to have failed to apply for the permits that would protect them from falling afoul of the current global ban on exports.

Western countries have repeatedly claimed that Assad has used chemical weapons, including sarin, against his own population since the Syrian Civil War began in 2011. In response to the most recent chemical attack, the US, UK and France launched coordinated air strikes against targets inside Syria aimed at destroying Assad’s asymmetrical warfare capabilities.

The strikes targeted a research centre, two chemical weapons facilities, and a regime command centre.