Five children found dead this week in a house in the north German village of Darry were suffocated, officials said after a post-mortem.

The mother of the children, who were aged between five and nine, is being held by police on suspicion of involvement in the deaths and has been placed in psychiatric care. The mother, 31, had turned herself in to police, saying the victims were all boys and had been drugged and then suffocated with plastic bags.

"At the moment we are assessing how responsible she could have been for this five-person homicide," senior prosecutor Uwe Wick said in the northern city of Kiel. He added he could not rule out that sleeping pills had been given to the children prior to their suffocation.

Police said yesterday they believed the mother, due to appear before a magistrate, may be mentally ill.

Darry, a town of 450 residents, is 40 km (25 miles) east of Kiel, near the Baltic Sea.

Chancellor Angela Merkel said more action was needed to help children in neglect. "Those in charge in the coalition, states and communities must do more to ensure children in neglect are better protected ... but it is also everyone's responsibility," she told German daily B.Z.

Spiegel Online reported teachers at the local school had told the youth welfare office about the run-down appearance of two of the boys. They had come to school without coats and shoes, according to neighbours. The magazine's online edition said workers from the local youth welfare office planned to visit the family yesterday, the day the children were found dead.