"Most children were brought in a very acute condition. There were no shortcomings in the treatment provided to them," she said.
The minister said teams from the health department and the School of Tropical Medicine have visited the hospital and collected samples.
Referring to the media persons present in the press galleries, Bhattacharya said: "The deaths were seemingly caused by toxins present in unripe litchis."
"But these toxins are not found in ripe litchis. I also appeal to the people not to consume unripe litchis. Children, particularly, should not be given unripe litchis.
Bhattacharya said such deaths had also taken place during the erstwhile Left Front regime.
"We have also seen such cases in Bihar's Muzaffarpur, where large amounts of litchis are grown," she said.
Immediately after the minister's statement, Leader of Opposition Surjya Kanta Mishra, a doctor who was health minister during the LF rule, said: "When such a case was reported when we were in power, we learnt it was caused due to pesticides applied on stalks of litchi trees".
"But now, we are getting some new information. After the incidents were reported earlier this month, it was said some virus was responsible. Now, today we were told it is due to the presence of a toxin in unripe litchis.
"I appeal to the government to take expert opinion so we can ascertain the reason behind the tragedy," he added.At least seven children between two years and four years of age died in Malda district between June 3 and June 7.
Hospital's vice principal-cum-superintending officer M.A. Rashid had then attributed the cause to a viral syndrome.