BANGKOK — 11 June 2026, A prominent Thai scientist said a mysterious powder believed to have contaminated noodle soup in northeastern Thailand was likely sodium nitrite, after hospitals treating affected patients were supplied with the antidote methylene blue.
The incident occurred in Udon Thani province, where at least 14 people fell ill after eating noodles from a local shop in Ban Phonsawan, Nong Na Kham subdistrict. Several patients required urgent hospital treatment.
Nopparat Phanset, director of the National Health Security Office’s Region 8 branch in Udon Thani, said the Ramathibodi Poison Centre had provided direct consultation to treating physicians on symptom assessment, diagnosis and antidote use.
The centre also coordinated the delivery of methylene blue to hospitals caring for the patients. Five patients with severe symptoms received the antidote promptly in line with medical guidelines, he said.
On 11 June, Jessada Denduangboripant, a science lecturer at Chulalongkorn University, said in a Facebook post that the use of methylene blue strongly suggested the contaminating substance was sodium nitrite.
“If methylene blue was sent as an antidote, then the powder mistaken for salt and used in the noodles was likely sodium nitrite,” he wrote, adding that the reported symptoms were consistent with sodium nitrite poisoning.
Sodium nitrite (NaNO₂) is a chemical commonly used as a preservative in processed meats such as sausages and Chinese-style cured pork sausages. It helps prevent bacterial growth and maintains a bright red colour in meat products.
However, excessive consumption can interfere with the blood’s ability to carry oxygen by causing a condition known as methemoglobinemia. Symptoms may include bluish discolouration of the skin, breathing difficulties and, in severe cases, rapid death.
Methylene blue is the primary treatment for methemoglobinemia. The medication helps restore the normal function of red blood cells, enabling them to transport oxygen effectively throughout the body.
Authorities have not yet officially confirmed the identity of the powder, and investigations into the incident remain ongoing.