XI'NING, March 10 -- Twenty-four people have been sent to hospitals with symptoms of poisoning after attending a wedding banquet Sunday in Xining, capital of northwest China's Qinghai Province, said local authorities on Monday.

As of Monday afternoon, eleven people were still receiving medical observation and three of them were in critical condition, said Yang Zhengping, director with the intensive care unit (ICU) of Qinghai Provincial People's Hospital.

Twenty-four people have been sent to two local hospitals with nausea, diarrhea, abdominal pain or vomiting after attending a wedding banquet in a restaurant in urban Xining on Sunday afternoon.

They have been given a preliminary diagnosis of suspected poisoning. Some have left the hospital in stable condition, said Yang.

The incident is under investigation by local police and health authorities.