Since then, symptoms ranging from nausea and anxiety to loss of consciousness have been reported in 546 patients admitted to hospitals. Many have recovered and returned home, while 148 are still being treated, said Dasari Nagarjuna, a government spokesperson.

Teams of experts have arrived at the city from India’s top scientific institutes. Different theories have been suggested and are being tested. The most recent hypothesis is contamination of food by pesticides.

“But nobody knows,” Prasadini admitted.