Six cases of the variant were also detected in neighboring Portugal this week.
Portuguese Health Minister Marta Temido said on Tuesday that there is a clear sign of “community transmission,” since the people infected had not traveled to the South Asian country.
Spain is investigating another suspected infection in Valencia, involving a woman whose sister had recently traveled to India.
On Tuesday, the World Health Organization said the variant has been detected in at least 17 countries.
WHO officials are still studying the variant, but said preliminary models suggest it could be more contagious.
The vast majority of COVID-19 infections in both Spain and Portugal are caused by the UK variant, which rose to dominance quickly on the Iberian Peninsula.
Even so, Portugal now has the lowest coronavirus infection rate in the European Union, reporting fewer than 70 infections per 100,000 people over the last two weeks.
Portugal is set to lift its state of emergency on May 1, though the country’s president Marcelo Rebelo de Sousa recently warned that the government “won’t hesitate” to reinstate it if the variants lead to another surge.
Spain’s infection rate is more than three times higher than Portugal’s, but the country saw its daily infections drop slightly on Wednesday compared to the same day last week.
The country is also gearing up to end its state of emergency on May 9.