RIGA: Rescuers in Riga retrieved bodies from a collapsed supermarket Friday and combed the rubble for survivors as the death toll from Latvia's worst post-Soviet disaster mounted to 45.

The roof of the Maxima supermarket smashed down on customers during peak shopping hours around 6:00 pm on Thursday in the Riga suburb of Zolitude.

Rescuers rushed to the scene, but many were themselves trapped when the roof caved in a second time.

“Everything was crashing down: the walls, the roof, everything!” witness Jana told LNT television in Riga, where flags were decorated Friday with black ribbons of mourning.

“I don't know what happened to the cashiers, if you were sitting down, there is no way you could have got out in time,” she said.

The tragedy shocked the small Baltic state, with the government declaring three days of mourning starting on Saturday and planning a moment of silence on Monday for its deadliest accident since regaining independence in 1991.

“We currently have 45 dead,” state fire and rescue service spokeswoman Viktorija Sembele told AFP. She said earlier that at least 40 other people were wounded when about 500 square metres of the roof caved in.

An Armenian citizen may have been among the victims, the Latvian foreign ministry spokesman said, citing unconfirmed information from state police.

Police refused to say how many people were thought to be inside the two-year-old building, and there were fears that teenagers could have been among them as a high school is near the store.

Maxima board member Gintaras Jasinskas told reporters 30 employees were in the store at the time: “Two of them are dead, two are in hospital and two others have not yet been found.”Also among the dead were three firefighters who were killed trying to rescue people following the first collapse.

“I am proud of my Dad, he died helping others, not thinking about himself,” a girl named Katrina whose father was among the dead said on social media.

'A very dangerous situation'

Around 200 rescue workers, backed by military personnel, combed through the rubble through the night and remained at the scene Friday.

Firemen searched through the rubble and soil by hand and with the help of five large cranes and could be seen through the crater in the roof.

“We are working at maximum capacity but it's a very dangerous situation in the building,” fire chief Oskars Abolins said.

Dozens of people gathered near the site, crying and holding out hope that their loved ones would still be found alive, even as more and more bodies were hauled out of the rubble and taken away in blue body bags.

“My son's friend is still in there. He worked in the store,” one woman told AFP through tears.

Visiting the scene, Prime Minister Valdis Dombrovskis said police had launched a criminal investigation to find the cause of the disaster.

“The state will do everything necessary to help the injured and pay compensation where it is appropriate,” he told reporters. Maxima said it would also offer compensation.

Speculation about the possible cause centred on plans to build a rooftop garden.

Local council official Juris Radzevics said that plans had been submitted to the council to turn the roof into a green area.

“The project was submitted in accordance with all regulations but of course we will be looking at whether materials and works were carried out to the proper standards,” Radzevics told the LNT television channel.

A police spokesman said emergency sirens had been set off in the store before the cave-in, adding that they were probing who sounded the alarm and why.

Run by the Lithuanian-owned Maxima chain, Latvia's number two retailer after Rimi, the supermarket was built in 2011 and was named one of the country's top three architecture projects that year.

Maxima published a statement on its website saying the company was “overwhelmed and shocked” by the disaster but that it was not yet aware of the cause and was providing “all the information at our disposal” to the authorities.