Georgetown Police Commander Clifton Hicken says the two children, a woman and a man apparently died yesterday shortly after sharing a bottle containing what was supposed to be a vitamin tonic.
The children were aged 9 and 6. Their relationship to the two adults is not immediately clear.
Hicken says detectives are searching for a person who dropped the bottle of the supposed tonic at the house.
Last year, three indigenous children fell ill in northwestern Guyana after eating candies containing cocaine. Police made no arrests in that case.