The exotic Lychee fruit is now a suspect behind a mystery illness.

Researchers say a toxin found in lychee fruit has been linked to a mystery illness that has affected children in India for years.

The US Centres for Disease Control and Prevention say outbreaks of the illness have coincided with the month-long lychee harvesting season in Bihar state since 1995.

The illness leads to seizures, altered mental state and death in more than a third of cases.