Thirteen people are now known to have died in the fire at the Teatre nightclub in the Atalayas area of the city of Murcia.
The fire broke out around 6am on Sunday. Initial information suggested that it started on the first floor, which is where bodies were found.
Four other people suffered smoke intoxication. There is still a search for people who are missing and who were part of a group celebrating a birthday. The number of deaths could yet rise.
Reports suggest that the fire was caused by a short circuit. The roof of the building collapsed after firefighters arrived.
Murcia's mayor, José, Ballesta told Spanish television: "We are devastated." Three days of mourning have been announced.
Spain's prime minister, Pedro Sánchez, has expressed his deepest condolences and said that the government will extend its support to the Murcia regional government.