CHENGDU -- A preliminary investigation showed that a suspected food poisoning case that killed two people in southwest China's Sichuan province was caused by nitrite, local authorities said Monday.

Thirty people developed symptoms of dizziness, nausea, vomiting, and stomach ache after eating breakfast at a funeral in Miaoya village, Bazhong City, Sunday morning, the municipal publicity department said.

As of 10 am Monday, two had died in hospital, three were in intensive care, and 25 were hospitalized but in stable condition.

Local disease control authorities tested food samples and patient vomit,confirming the sickness was caused by nitrite poisoning.