Two girls aged nine and 10 were forced to swallow a glass of water containing a drug by their father at Pillar Point Vietnamese refugee centre in Tuen Mun yesterday.
The girls' aunt went to their rescue after Chau Chun-bau, 30, who had also taken the drug, passed out.
They were taken to Tuen Mun Hospital where the girls were in satisfactory condition and Mr Chau stable last night.
The drug powder left behind was taken to a government lab for examination.
A police source said the man had had an argument with his wife on Sunday after she accused him of having a mistress. The woman took their five-year-old son and said she was leaving him, the source said.
The unemployed man reportedly swallowed the drug powder in the early hours of yesterday in an apparent suicide attempt.