The World Health Organisation (WHO) is investigating whether there is any connection between manufacturers whose contaminated cough syrups it has linked to the deaths of more than 300 children in three countries, a person familiar with the matter told Reuters.

Citing “unacceptable levels” of toxins in the products, the WHO is seeking more information about the specific raw materials used by six manufacturers in India and Indonesia to produce medicines linked to the recent deaths, as well as whether the firms obtained them from some of the same suppliers, the person said. The WHO has not named any suppliers.