The 46-year-old woman, who has not been named, died in the early hours of Sunday after having a meal with her husband and son at the Riff restaurant in the eastern city of Valencia.
Regional health authorities say 30 people – including the woman, her husband and son – fell ill with food poisoning after eating at Riff between 13 and 16 February. The woman’s husband and son are recovering.
A judge in Valencia has opened an inquiry into the death and is awaiting the results of a postmortem and an analysis of samples taken from the restaurant.
The regional high court told the Europa Press news agency that no individuals were currently under investigation.