A woman has died and 28 more diners fell ill after eating at a Michelin-starred restaurant in Spain.

The diner went to RiFF in Valencia with her husband and son, 12, both of whom also had diarrhoea and vomiting.

The restaurant is now closed while public health officials investigate the exact cause of the outbreak.

RiFF, which has one Michelin star and is described by the guide as serving "innovative cuisine", has issued an apology to its customers.

Officials tracked down 75 people who ate at the restaurant between 13 and 16 February and learned that a total of 29 had suffered food poisoning, including three families.

This included a 46-year-old woman who ate out with her family on Saturday night and died at home in the early hours of Sunday morning.

A spokesperson from Valencia's regional ministry of health told BBC News that food safety officers inspected RiFF on Monday but were unable to find an obvious cause.

Samples of some of the dishes that were served as part of a tasting menu have now been sent to the National Toxicology Institute for analysis, they added.

Some reports have suggested that morel mushrooms may have been to blame, but officials told local media they were waiting for the test results to come back before singling out any particular ingredient.

RiFF's owner and head chef Bernd Knöller said in a statement that he was working with health officials to establish the facts.

"Regardless of the reason that may have caused this situation, I want to convey my deep regret for what happened, hoping that soon all these facts can be clarified," he added.

"I have made the decision that the restaurant remains closed until the causes of what happened are established."