The authorities in Valencia are investigating the death of a woman who had eaten at a Michelin-starred restaurant, its owner said this week, as Spanish news outlets reported that the establishment had been tied to as many as 28 other cases of food poisoning.

The restaurant, RiFF, has closed indefinitely as regional health officials investigate.

Bernd H. Knöller, the owner and head chef of RiFF, said in a statement that the restaurant would be closed until “the causes of what happened are established and we can resume work with full guarantees for both the staff and customers.”

He said the decision was based on what he had learned from Valencian health authorities about “different gastric illnesses in several customers of the restaurant, including the death of one.”

Mr. Knöller said that he had offered his “full collaboration” with the investigation by the regional Ministry of Health to determine what caused the death. The woman, who has not been publicly identified by the authorities, died at her home on Sunday morning, the restaurant said in an emailed statement.