Update at 8.15 a.m EST: At least 45 people -- including three firefighters -- were killed and dozens more injured and trapped after the roof of a shopping market in Riga, Latvia’s capital, collapsed, Latvian news agency LETA reported on Friday. The tragedy has become the nation’s worst disaster since it regained independence in 1991.

Rescue workers recovered 45 bodies from the debris of the Maxima store, which collapsed Thursday evening, and 28 of the 36 people injured in the incident were hospitalized, LETA reported.

Rescue work continued throughout night, and firefighters pulled victims out of the mangled ruins of steel, concrete rubble and shattered glass using cranes and other equipment to clear the debris. 

Authorities expect the death toll to rise as several more people are feared trapped under the debris.

According to local media reports, a portion of the Maxima supermarket’s roof, located in a residential suburb of Riga, collapsed at about 5.45 p.m. local time, when the store was busy with people shopping on their way home from work.

A second collapse occurred about 20 minutes later, bringing down another part of the roof and trapping rescue workers.

"Three of them were state fire and rescue service officials," Viktorija Sembele, a spokeswoman for Latvian rescue services, told BBC News. "Overall, eight firefighters have been injured."

It was not clear what caused the collapse, but authorities are probing possible violations of construction laws. The building opened in 2011, and it reportedly received an award for its architectural excellence at the time.

"It is clear that there has been a problem with fulfillment of construction requirements," Rihards Kozlovskis, the interior minister of Latvia, said.

According to local media reports, a garden was being constructed on the roof of the building, and the weight of the soil possibly weakened the roof.

Rescue work may take a long time as it is not clear how many more are trapped under the rubble, officials told Reuters.

"As we have to search all the rubble and the whole construction, rescue work might continue for another day," Oskars Abolins, chief of state fire and rescue services, told Latvian TV.