Latvia’s president has demanded that a supermarket cave-in that killed at least 53 people be treated as murder, while rescuers and investigators combed the ruins for bodies or clues.

Terrifying accounts emerged from survivors of the cave-in at the Maxima store in the capital Riga on Thursday, as anger and suspicion mounted over its causes.

“I was queueing at the cash desk when the roof suddenly caved in. It all happened within a few seconds,” said 19-year-old Antons Ryakhin, saying “about 100 people” had been inside with him.

“It was dark but still light enough to see the exit. I ran out. The doors were open, but a lot of rubble fell in front of them – I think that’s why some people couldn’t get through.”

A police spokeswoman said 13 people were still reported missing in connection with the collapse, the Baltic state’s worst disaster since independence in 1991.

But two days on, hope is dwindling of finding more survivors.

President Andris Berzins told Latvian public television the disaster “must be treated as the murder of many unprotected people”, calling for it to be “investigated at maximum speed”.

Police investigators could be seen sifting through the rubble alongside rescuers at the site, where the latest body was hauled from the mass of tangled steel and concrete Saturday at dawn.

“Much of the site has been checked but the structures that remain include some of the largest, heaviest blocks which are particularly dangerous,” fire and rescue service spokeswoman Viktorija Sembele said.

Latvia declared three days of mourning following the disaster, and flags were being flown from houses across the country with a black sash attached.

Speculation as to its causes has centred on the extra weight created by a rooftop garden and playground, and on the possibility that building regulations may have been bent.