At least 51 people are known to have died when the roof of a supermarket in Riga, Latvia collapsed on Thursday night, BBC News reported. Rescue efforts have continued through Friday, as Latvian police launched a criminal investigation into the collapse, news reports said.

"It is the deadliest disaster in the former Soviet republic since it became independent in 1991. Police expect the death toll to rise further," BBC News reported.

The store had been filled with shoppers when an a big section of the roof caved in. When rescue workers began searching for survivors, a second and larger section caved in, which trapped and killed them, The AP also reported.

"It felt like an earthquake. They loaded so much material on that roof over the past two weeks that I simply don't understand," said Nina Kameneva who is a retiree who lived near the supermarket, as reported by The AP.

"About 500 square meters (5,300 square feet) of the roof collapsed, the rescue service estimated, destroying large sections of the store's high walls and nearly all its front windows," The AP also reported

The building structure "once [been] vaunted as a place where high-rise residents could step out of their homes, stroll along a shady garden and pick up a couple of items for dinner," The Associated Press reported.

"In recent years due to the economic crisis many institutions, including construction oversight, ... were closed in Latvia in order to save money," Deputy Mayor Andris Ameriks told Latvian television, according to the AP.

Latvia's government declared three days of mourning will begin in honor the fallen.