Maria Jesus Fernandez Calvo, 46, died on Sunday after a bout of vomiting and diarrhea following a birthday meal with her husband and 12-year-old son at Valencia’s RiFF restaurant.
It is understood that all three suffered vomiting and diarrhea within hours of consuming a tasting menu on Saturday, but while the husband and son recovered, the woman died in the early hours of Sunday.
It has since emerged that 26 other diners also reported feeling unwell after eating in the restaurant, according to a report in the online newspaper Público, although their symptoms were milder.
Health authorities are exploring whether a morel mushroom risotto is the cause of the outbreak and the possibility that the dish mistakenly included a highly toxic funghi that looks similar to a morel.
The deadly 'false morel' is very similar in appearance to the morel mushroom but is highly toxic.
Head chef, Bernd H. Knöller, closed the restaurant on Monday morning to allow public health officials to carry our a full investigation.
Investigators did say that there were no apparent hygiene problems that could have contributed to food poisoning but that samples of ingredients and raw food products included in the menu would be sent for analysis.
“We will have to wait for the autopsy to be carried out on the woman before we can determine whether it was the ingestion of a food that directly caused her death, or whether it prompted a state that led to this fatal outcome, or if she had an existing condition,” explained regional health chief Ana Barceló.
Forensic teams will work to determine her death was caused by the poisoning or whether she may have choked on her own vomit or had a pre-existing condition exacerbated by the illness.
RiFF was opened by Knoller in 2001 and awarded a Michelin star in 2009.
It features a €135 ($153) tasting menu including black truffle, imperial caviar and lobster.