Interior Minister Rihards Koslovskis said the number of dead was 32, more than five times more than the previous tally of six.
Three firefighters were also killed in the tragedy
Thirty-five people were also injured in the tragedy. The authorities could not confirm the reason behind the roof collapse.
Three firefighters were also killed while 10 rescue workers were among the injured.
Television images showed the roof of the 500-square metre supermarket complex collapsing in two stages.
Latvian Prime Minister Valdis Dombrovskis said the police had launched a criminal investigation to understand the reason behind the tragedy.