Children die in Bihar state from a deadly brain disease believed to be linked to a toxic substance found in the fruit.

Dozens of children have died in the northern Indian state of Bihar this month from a deadly brain disease believed to be linked to a toxic substance found in lychee fruit.

Health officials on Wednesday told AFP news agency that at least 31 children died in the past 10 days, while Indian media reports on Thursday cited at least 43 such deaths.

Most deaths were reported from two hospitals in Bihar’s Muzaffarpur district, famed for its lush lychee orchards, officials said.

The deceased children showed symptoms of acute encephalitis syndrome (AES), senior health official Ashok Kumar Singh told AFP news agency, adding most had suffered a sudden loss of glucose in their blood.

“The health department has already issued an advisory for people to take care of their children during the hot summer when day temperature is above 40 degree Celsius,” Singh said.

At least 40 other children complaining of similar symptoms were being treated at intensive care units.

“We are trying our best to save them,” said SP Singh, the chief medical officer of Sri Krishna Medical College and Hospital.

The outbreak of the disease has been happening annually during summer months in Muzaffarpur and neighbouring districts since 1995, typically coinciding with the lychee season.

Known locally as Chamki Bukhar, the disease had claimed a record 150 lives in 2014.

In 2015, US researchers had said the brain disease could be linked to a toxic substance found in the exotic fruit.

They also said more study was needed to uncover the cause of the illness, which leads to seizures, altered mental state and death in more than a third of cases.

Outbreaks of the neurological illness have also been observed in lychee-growing regions of Bangladesh and Vietnam.