Four children from an extended family in southwest China's Yunnan Province were confirmed dead and two other members of the same family were still in critical condition Tuesday in an apparent poisoning case, the local government said.

The four dead, all male, were cousins aged from 18 months to 14 years, said a spokesman of the Menghai County government in Xishuangbanna.

The boys' only caregiver was their grandmother, 73-year-old Chen Yongzhen, he said.

Chen and her seven-year-old granddaughter, were still in a comma Tuesday.

Doctors with Daluo Township Hospital said the family sought medication at midday Monday. The four boys did not respond to emergency treatment and died at around 1:40 pm.

Chen and the girl were sent to a hospital in downtown Xishuangbanna Monday evening.

Police and health authorities suspected the deaths were caused by poisoned food and samples of the remnant food in the house had been sent for lab work.

"We suspect Chen had mistakenly used nitrite for salt when she was cooking lunch," said the county's public security chief Feng Xiaodong.

One of the family's grandchildren, a boy, was unharmed because he skipped lunch Monday, said Feng.

The children's parents all work as rubber farmers in Myanmar, mailing home a meager 70 yuan every week, which is hard to cover all the family's expenses, he said.

The old woman used to search for useful items in the neighborhood's waste dump.

The investigation is continuing.

(Xinhua News Agency May 20, 2009)