One woman has died and 28 people have suffered food poisoning after eating at a Michelin-starred restaurant in the eastern Spanish city of Valencia.

The 46-year-old woman, who has not been named, became ill after having a meal at the Riff restaurant with her husband and son. She died in the early hours of Sunday. Her husband and son are recovering.

Health authorities in the city have so far tracked down 75 people who ate at Riff between 13 and 16 February, and have confirmed a total of 29 cases of food poisoning.

“With the exception of the person who died, all those who fell ill have shown light symptoms – mainly vomiting,” the regional health authority said in a statement on Thursday.

It said food safety officers had visited the restaurant on 18 February and had failed to find any obvious explanation for the poisonings. Samples of dishes served as a part of a tasting menu were taken and are being analysed by the National Toxicology Institute.

A spokeswoman for the Valencian health ministry declined to comment on reports that a species of mushroom may have been the source of the outbreak of sickness, saying the analysis was still being carried out.

Bernd H Knöller, the head chef and owner of Riff, offered his deepest condolences and said he was collaborating with the regional health authorities to determine exactly what had happened.

“I’ve taken the decision to close the restaurant until we know the precise causes and can reopen with the necessary guarantees for the safety of both staff and customers,” Knöller said. The chef added that preliminary inspections had found that the restaurant had complied with the necessary health regulations.

Riff, which has one Michelin star, is described by the guide as offering “innovative cuisine … based around the highest quality, seasonal, local products to create successful culinary combinations and interesting set menus”.