An unnamed middleman in Mumbai provided a crucial raw material used in Indian-made cough syrups that have been linked to the deaths of more than 70 children in Gambia, a chemicals trader involved in the supply chain said.

The World Health Organization said last year the syrups, made by Indian manufacturer Maiden Pharmaceuticals, contained lethal toxins ethylene glycol (EG) and diethylene glycol (DEG) — used in car brake fluid. These ingredients can be used by unscrupulous actors as a substitute for propylene glycol (PG), which is a key base of syrupy medicines — because they can cost less than half the price, as it was reported in March.

The children who died were mostly under age 5 and died of acute kidney injury, some within days of taking the syrups.