International inspectors have found traces of banned toxic chemicals in at least three military locations in Syria, four diplomats and officials said, less than two years after President Bashar al-Assad agreed to dismantle the country’s chemical arsenal.

Traces of sarin, a nerve agent, were found in drainage pipes and in artillery shells in two places, and traces of another banned toxin, ricin, were found in a third location, a scientific research center, according to a United Nations diplomat, who spoke on the condition of anonymity to discuss confidential reports from the inspectors.

The discovery of the small amounts of banned materials, first reported byReuters, comes as Syrian government forces are being accused of continuing to bombard insurgent-held areas with chlorine bombs. […]