The head of the Palma fire service, Eder Garcia, said the restaurant floor had collapsed onto the bar below, which is “where we found the most victims”.
“The causes are being investigated. The first hypothesis is that it was possibly due to excessive weight,” he told reporters at the scene, adding the building has “an old structure”.
A technical team was at the site on Friday to determine the cause of the collapse.
Santiago Aranga, a local who was walking his dog across the street from the seafront venue at the time of the accident, said he heard a “boom” that sounded “like a bomb”.
“There was screaming, crying, hysterics,” he told television station TRECE.
Most people in the area were German tourists and “it was very difficult to try to calm them down, to pull people out in another language. I don’t understand or speak German,” he added.
‘Lot of commotion’
Another local resident, Vicky Garcia, said the venue had only recently reopened after being refurbished.
“We heard a roar, then a lot of police, a lot of firemen, a lot of commotion,” she told local television IB3.
Speaking at a business forum in Barcelona, Spanish Prime Minister Pedro Sanchez conveyed his condolences to the victims’ families.
“I would also like to express my best wishes for a speedy recovery to the injured,” he added.
Mallorca is known for its pristine waters and beaches, and the Balearic Islands attract more tourists than all other Spanish regions except Catalonia.
More than 14 million tourists visited the islands last year, according to official figures.
Thursday’s collapse took place at the start of the archipelago’s peak tourist season, on a beachfront avenue home to several shops and entertainment venues.
A 2009 collapse of a three-story building in Palma de Mallorca killed seven people, including three Colombians and two Germans.