Early reports suggest the roof caved in due to either faulty construction or building work on its grass- and gravel-covered surface, where workers were installing a garden area and children's playground for an adjacent high-rise residential building.
President Andris Berzins spoke bluntly about the disaster at the Maxima supermarket in Riga, though he did not single anyone out as culpable.
"This is a case where we need to say clearly it is the murder of an enormous number of defenseless people, and that's how we should proceed," Berzins said in an interview with Latvian television.
Fifty-four deaths had been confirmed from the structural failure by today afternoon. Police spokesman Dairis Anucins said earlier that there were reports of 10 missing people, and it was not clear if the new death toll included any of them.
Laila Rieksta-Riekstina, head of the state's child welfare department, told Latvia Radio that 16 children lost parents in the accident. Three of them lost both parents. Some 40 people were injured, including 13 firefighters who rushed to the scene, and 23 people remained hospitalised as of today afternoon, police said.
The Fire and Rescue Service said only 80 square meters (850 square feet) of debris remained to be searched as of late today afternoon, but they said it was a difficult section with rubble piled up to 4 meters (12 feet) high. Rescue workers had stopped the operation early today to consult with engineers before continuing.