A family of four in India died under mysterious circumstances after a late-night meal that included watermelon, leading to panic in the area and the subsequent drop in sales of the popular summer fruit.

In the early hours of Sunday, 27 April, Abdullah Dokadia, 45, his wife Nasreen, 35, and their daughters Ayesha, 16, and Zainab, 13, died at their home in Pydhonie, in south Mumbai's Bhendi Bazaar area.

The family had hosted nine guests for dinner that evening and served biryani. After the relatives left, the four ate watermelon at around 1am. By 5am all were severely ill with vomiting, stomach pain, and diarrhoea, and were rushed to a local hospital in a semi-conscious state. They died within hours of each other. None of the dinner guests, who had eaten the same pulao earlier in the evening, fell ill.

Police registered a case of accidental death and have recorded the guests' statements.

But soon after, traders say the demand for watermelon fell nearly 30 per cent, with the fruit being offloaded for as little as five to seven rupees (4p to 5p) per kilogram – a fraction of its usual wholesale price of between 10 and 35 rupees (8p to 27p), according to Indian media reports.

Retail prices for watermelon in Mumbai normally range between 30 and 100 rupees (23p to 78p) per kilogram.

Vendors at Crawford Market in south Mumbai told The Indian Express customers were returning watermelons they had already purchased, after social media posts about the death of the family stoked fear.

The Maharashtra Food and Drug Administration (FDA) collected several samples of biryani, watermelon, stored drinking water, rice, chicken, dates and spices from the family's residence for laboratory testing, News18 reported. The viscera of all four victims have been sent for chemical analysis and the final forensic report is still awaited.

Doctors have said fear-mongering theories on social media about watermelons had no scientific basis. Dr Sanjay Surase, medical superintendent of Sir JJ Hospital where three of the victims died, said the clinical picture did not match food poisoning.

"The speed of deterioration, the severity of the condition, and the fact that multiple members of a single family were affected are not consistent with a routine food-borne illness. We are looking at the possibility of a toxic or chemical substance," he told The Indian Express.

The state food safety commissioner separately told the newspaper that even high levels of pesticide residues on the watermelon could not have caused such deaths, as fruits are routinely treated with multiple pesticides before harvest without fatal consequences.

The fruit is sourced from farms across Maharashtra, Karnataka and Gujarat, and growers across all three states are watching the panic with alarm. The Maharashtra FDA said no direct link between the deaths and watermelons had been established and that no conclusions would be drawn until scientific confirmation was received.

Police said they were also investigating whether the family had been under any financial or psychological stress in the period before the deaths.