Twenty-two children who were placed in the care of the state died in an eight-year period as a result of suicide, manslaughter, drug overdoses and natural causes, new figures reveal.

Between 2000 and 2008, four young people died from suicide, five from drug overdoses and one was killed by a third party, leading to a manslaughter conviction, according to information released to the Sunday Tribune under the Freedom of Information Act.

In the same period, one child died from heart problems relating to Down Syndrome, another from cancer, two from leukaemia and one from an asthma attack while asleep. One child died from the complications of a severe disability; another young person died from a brain tumour, and another died during an operation. One young person was killed in a hit-and-run accident and another had a brain seizure.

Last year, two children in the care of the state died, one from leukaemia. The HSE refused to provide details of the circumstances of the second death. It said a "critical incident review" was carried out following the child's death and that the forthcoming inquest should provide some answers about how the child died.

Several children who died from overdoses in recent years were in emergency care. Social workers have voiced concerns that the system is failing vulnerable young people.

The deaths of certain children in care have been investigated, but no report has yet been formally published. They include Kim O'Donovan (15) , who was found dead at a city-centre B&B from a suspected drug overdose; David Foley (17), who died from an overdose three years after he voluntarily sought care from the state; and Tracey Fay (18), who was found dead after injecting herself in 2002. All had sought more support from health authorities.

Melissa Mahon (14) was killed in 2006 by Sligo man Ronnie Dunbar while she was in HSE care. He was found guilty of her manslaughter in May.

It emerged last week that a unit that cares for the needs of young people with serious emotional and behavioural problems is to be closed down. The 24-bed special care detention unit at Ballydowd, Palmerstown, Co Dublin, will be closed following a report into standards at the unit by the Health Information and Quality Authority. The unit, which houses 12 children, was opened in 2000 at a cost of €13m.