Twenty three students of Orong Higher Secondary School have been admitted in the Samdrupjongkhar hospital last evening with swelling, loss of feeling and numbness in the leg.
Earlier this month, two students died with similar symptoms.
Of the 23 admitted, two are in serious condition.
The Dzongkhag Medical Officer said they are responding well to the treatment.
They are currently being given vitamin injections, nutritional rehabilitation and physiotherapy.
He said it is possible that the students are suffering from lack of proper nutrition.
A special team from Thimphu will arrive tomorrow in Samdrupjongkhar for investigation.