Is it permissible to give children infant formula containing vitamin "thiamine" (B1), while doubting its source and whether it is plant-based or animal-based (especially from pork), due to the inability to ascertain its source?

Milk suspected of containing parts of a pig should not be given to children. It is forbidden if the impurity is confirmed to be present, unless the impurity has been treated and transformed into another substance before being mixed with the milk. It is advisable to avoid this type of milk as long as there is no necessity, and to seek an alternative.