Chemical residue from pesticides could be behind a mysterious illness that affected hundreds in Andhra Pradesh's Eluru, say tests by AIIMS in Delhi and other scientific facilities across the country.
These tests suggest organochlorines, or even organophosphates, could be the reason for the illness; pesticides could account for the chemicals' presence.
Experts, however, say the exact reasons can only be identified after analysing food, water and vegetable samples over the next few months.
Chief Minister Jaganmohan Reddy held a video conference with state officials, who were told to take action to ensure such outbreaks are not repeated.
These actions include cracking down on dumping grounds and regular testing of food, soil and water samples. The Agriculture Department was told to withdraw harmful pesticides and encourage farmers to opt for organic alternatives.
Eluru is the headquarters of the West Godavari district, which is seen as the state's "rice bowl" and extensive paddy cultivation has led to the heavy use of pesticides and fertilisers.
Mr Reddy also called on AIIMS (All India Institute of Medical Education) and IICT (Indian Institute of Chemical Technology) to conduct a long-term study on the Eluru outbreak.
AIIMS had said lead had been detected in blood samples of around 30 individuals. Nickel, another potentially toxic chemical, was found in milk samples taken from patients' houses. Preliminary tests also showed lead in blood samples of patients' family members.
IICT experts said no trace of heavy metals - lead, nickel or arsenic - or pesticide residues were found in 21 drinking water samples. However, endosulfan (an organochlorine insecticide) and DDT (another harmful pesticide) were found in blood samples.
Lead was also found but no trace of organophosphates were found, they said.
Hyderabad's National Institution of Nutrition reported pesticide residue in tomato and brinjal samples. Tests by the Center for Cellular and Molecular Biology in Hyderabad and the National Institute of Virology in Pune found no evidence of bacterial or viral infection.
Tests on air quality by the National Environmental Engineering Research Institute (NEERI) in Hyderabad found pollution within permissible limits. NEERI also tested underground water and surface water samples, and found all metals to be within permissible limits, except for mercury.
Tests showed levels of mercury to be higher in underground water samples than those from surface sources. Scientists said this could be due to solid waste burning.
The World Health Organisation (WHO) has said it is critical to establish how pesticide residues are entering the body.