Latvia’s previous most deadly accident was a nursing home fire that killed 26 people in 2007.
Rescue Service spokeswoman Viktorija Sembele earlier said 35 people had also been injured in Thursday’s collapse at the Maxima supermarket, in western Riga.
Three firefighters were among the dead, and a toddler was among those injured.
Search teams continue to comb the rubble for more bodies, with the number of dead expected to rise, Sembele said.
“The firefighters are still working to find people, they are putting away the constructions and still approximately 600 square meters of this collapsed area should be searched through,” she said.
Sembele declined to speculate on the cause of the collapse.
“There are a lot of versions, a lot of stories. The real cause of this tragic accident will be investigated by state police and other authorities once the rescue is finished.”
Riga Mayor Nils Usakovs told CNN that authorities think building materials stored on the roof caused it to collapse.
Latvia’s Ministry of Foreign Affairs said some of the victims of the collapse had not yet been identified.
“Police (are) currently working at the scene to identify the dead; for victim identification, police officers are also cooperating with relatives who gather on the site,” . It asked relatives of anyone missing to call emergency services.
European Commission President Jose Barroso issued a message of condolence after the collapse.
“I am deeply saddened by the terrible tragedy,” he said.
“Please convey my expression of deepest sympathy and solidarity to the families of the victims and those who lost their lives in rescuing people as well as to all those affected by this tragic accident.”