The BBC's Nichola Carroll: "People stopped in the streets - they could hardly believe what they had seen"
At least 21 people have died and more are feared missing after the roof of a supermarket in the Latvian capital Riga collapsed.
Rescue efforts continued through the night and police have launched a criminal investigation.
Three of those killed were emergency workers who were helping people trapped when more of the roof came down.
The cause of the collapse is unclear although reports say a garden was being constructed on the roof at the time.
The supermarket, which opened in 2011, is part of the Maxima retail chain.
"The police have started the investigation already," said Prime Minister Valdis Dombrovskis after visiting the scene.
"The criminal process has started about violating construction norms."
This injured fireman was pulled from the rubble
The store was said to have been busy when the roof fell in
A view from a nearby building shows the extent of the collapse
People have been waiting for news at the scene
Latvian rescue services spokeswoman Viktorija Sembele said early on Thursday that emergency workers were among those killed.
"Three of them were state fire and rescue service officials. Overall eight firefighters have been injured," she said.
Earlier, officials said that at least 35 people had been injured.
TV footage showed rescue workers using mechanical cutters to clear debris from the single-storey concrete and glass building. Cranes were brought in to remove slabs of concrete.
More than 60 soldiers were helping the rescue effort, the army said on its official Twitter feed.
The initial collapse happened just before 18:00 (16:00 GMT) on Thursday, when the store was busy with customers.
Walls and windows also crumbled, leaving the shell of the building piled with rubble, witnesses said.
About 20 minutes later another part of the roof caved in, trapping rescue workers who were trying to reach survivors.
The rescue services believe a total of about 500sq m (5,300sq ft) of roof caved in, according to reports.
Witnesses said customers tried to run out after the first part of the roof collapsed but the supermarket's electronic doors closed, trapping them inside.
Normunds Plegermanis, deputy head of rescue services, said emergency teams faced difficult conditions.
"Falls are happening from time to time... it is very dangerous to work inside," he said.
The reason for the collapse is not known. However, the BBC's Caucasus correspondent Damien McGuinness says a possible explanation is the weight of soil being used to plant a winter garden on the supermarket's roof
