By Monday afternoon some 2020 people had been treated for symptoms including nausea, abdominal pain, vomiting, diarrhea and fever in the cities of Tarragona and Barcelona, confirmed the Catalonia health authority.
The outbreak, discrobed as "a norovirus infection" has been blamed on contaminated bottled water of the type used in office water coolers and tests are being carried out to identify the source.
"The possible source of contamination could be spring water bottled at a plant in Andorra," explained Catalonia's regional health department in a statement.
"We are working with authorities in Andorra to determine the causes of the outbreak."
The bottled water company Grupo Eden Springs said it had identified the suspected source and recalled 6,158 bottles that had been distributed in Barcelona and Tarragona to 925 clients as "a precautionary measure".
"We are withdrawing six pallets of bottled water from the Font d'Arinsal source in Andorra while the proper investigations are carried out," said a statement from Antonio Alarcon, the manager of the Grupo Eden Springs.
"We deeply regret this incident and any inconvenience it has caused our customers," said the company on its Twitter account.
Lamentamos profundamente este incidente y las molestias que el mismo pueda ocasionar a nuestros clientes https://t.co/8FMKpaTjCy— Agua Eden (@agua_eden) April 16, 2016