Hong Kong  - A Hong Kong mothers was in police custody Thursday for the suspected killing of her two children who were found dead in their smoke-filled flat.

Police said the children, a 13-year-old boy and a 12-year-old girl, were found Wednesday afternoon after their mother called them to say the children were unconscious after she burned charcoal in the flat.

It later emerged that fire officers and police had visited the flat 13 hours earlier after a neighbour reported smoke coming from the flat.

But both crews left after the mother claimed she was burning incense and did not want the children disturbed from their sleep.

Police said the woman, 38, is believed to have lit the charcoal after arguments with her married lover, the father of the children, who also lived in the flat in the Tuen Mun district.

She was found in a semi-conscious state by fire officers who broke into the flat after her call to the police.

The children were both unconscious but were declared dead at the scene. Autopsies were to be carried out Thursday.

The incident is the latest in a series of family tragedies in the city of 7 million people, many of them in the Tuen Mun area.

Charities and support groups working with families in crisis blame the widening gap between rich and poor and the high-stress levels of families trying to cope with the economic downturn.

There have been eight deaths involving five families so far this year. These include a 2-year-old girl who was thrown in January out of a ninth-floor window by her uncle who then jumped to his death.

In April, a 79-year-old woman stabbed her husband to death and then killed herself, and in May, a 50-year-old woman beat her elderly mother to death with a hammer. (dpa)