As many as 14 agencies working to ascertain the nature of the mysterious illness in Eluru, the district headquarters of Andhra Pradesh's West Godavari, are yet to zero in on the exact cause and some of them on Friday indicated that they needed more time.
"National Institute of Nutrition (NIN) has also found the presence of organophosphate in blood samples and requires some more time for further investigations," West Godavari Joint Collector Himanshu Shukla said in a statement.
The All India Institute of Medical Sciences, New Delhi, has tied up with other institutions to study the presence of organochlorine and organophosphates in the blood of the affected people.
As part of investigations on several samples, AIIMS found the presence of lead and nickel only in two of the 40 urine samples.
"AIIMS and the Indian Institute of Chemical Technology (IICT) have not found anything adverse in the water samples and claim that water is unlikely to be the source," said the statement.
Experts from Hyderabad-based NIN asked time till Monday to further analyse water samples, which were found to be laden with pesticide Organochlorine.
However, officials claimed that Eluru water was found to be potable and "absolutely fit for human consumption".
In food samples such as vegetables, NIN detected herbicides which are incidental to the study.
"Other results relating to vegetables, rice, fish, meat and soil are under analysis and the results will likely be available by the coming Wednesday," said the note.
Meanwhile, the number of cases reached 616 by Friday evening, but only six of them were active cases, and even two of these were ready to get discharged.
On Friday, only four cases were admitted till 7 pm while a total of 576 patients have been discharged.
Until now, only one patient succumbed to the illness.
Symptoms of the mysterious illness had included three to five minutes of epileptic fits without repetition, forgetfulness, anxiety, vomiting, headache and back pain.
Eluru, which is 58 kilometres north-east of Vijayawada, is a coastal paddy cultivation and aquaculture hub.