Health authorities in Andhra Pradesh's Eluru town sounded an alert on Sunday as over 200 people were hospitalised since Saturday night with symptoms resembling epilepsy.
While 140 people admitted to various hospitals on Saturday were discharged, about 90 more people reported sick on Sunday.
About 50 people were brought to Government Hospital Eluru with symptoms of nausea and fainting. Another 60 people were admitted to private hospitals.
They were brought to hospitals with symptoms like suddenly collapsing, frothing at mouth and shivering. Those who were hospitalised on Saturday night were discharged on Sunday morning after they recovered.
Doctors said the condition of all were stable. Two people were shifted to Vijayawada due to their worsening condition.
Medical and health experts were trying to ascertain the cause of sickness. Most of the affected people were elderly and children.
Authorities were baffled as the affected people were neither related nor they had attended a common event.
According to officials, the cases were reported from different areas in Eluru town of West Godavari district.
Experts were analysing the cases. The blood samples of those reported sick were also collected but the reports were found normal.
Health Minister Alla Nani, who visited the Government Hospital and called on the people undergoing treatment, said their Covid-19 samples were also tested and none of them found positive.
He said 150 beds in Eluru and 50 beds in Vijayawada were kept ready for any emergency. "The government is taking all necessary steps. There is no need for any panic," he said, adding that Chief Minister Y.S. Jagan Mohan Reddy was personally monitoring the situation.
Alla Nani directed medical and health officials to conduct door-to-door survey to find out if the affected people had used contaminated food or water.
The health authorities have also been asked to ensure availability of emergency medicines to deal with any situation.