At least 64 people have died in a fire that engulfed a shopping and entertainment complex in the Siberian coal-mining city of Kemerovo.
Many of the victims are children. Ten people are still listed as missing.
The blaze started on an upper floor of the Winter Cherry complex during school holidays. The mall's shops, cinema and bowling alley were packed at the time.
Video posted on social media showed people jumping from windows to escape the flames.
"According to preliminary information, the roof collapsed in two cinemas," Russia's Investigative Committee said in a statement.
The cause of the fire is not yet known. The authorities have launched an investigation.
Four people have been detained for questioning, including the head of the company that manages the shopping centre, according to the Investigative Committee. The owner of the Winter Cherry complex is among those being held.
What do we know so far?
The fire broke out at about 17:00 (10:00 GMT) on Sunday. Some 660 emergency personnel were deployed in the rescue effort.
Firefighters said the building was still smouldering a day later, with smoke billowing out and the remaining structures at risk of collapse.
The region's deputy governor Vladimir Chernov was quoted as saying the fire probably began in a children's trampoline room.
"The preliminary suspicion is that a child had a cigarette lighter which ignited foam rubber in this trampoline room, and it erupted like gunpowder," he said.
However, Rossiya 24 TV, a national broadcaster, said an electrical fault was the most likely cause - as in most previous deadly fires in Russia.
Russia's commissioner for children's rights, Anna Kuznetsova, has blamed negligence, and called for urgent safety checks at similar entertainment complexes.
Two witnesses told BBC Russian that they had seen the fire blazing in the trampoline room on the fourth floor but had not heard any fire alarm.
Meanwhile, witness Anna Zarechneva told Russian RBC News that "a woman burst into the cinema during the film and shouted 'Fire! Fire!', and we started running out".
"The lights didn't come on in there to help us escape. We got out by following the floor lighting. But at that point no alarm bells were ringing. I only heard an alarm when I reached the first floor."
Who were the victims?
At least nine of the bodies found so far are children.
As well as those killed, 11 injured victims are being treated in hospital, suffering from smoke inhalation.
The most serious case is an 11-year-old boy whose parents and siblings died in the fire, Health Minister Veronika Skvortsova said. He reportedly fell from the fourth floor and is in intensive care with multiple injuries.
An Instagram post from Kemerovo showed a big queue of volunteers waiting to donate blood at a clinic.
Kemerovo, a key coal-producing area, lies about 3,600km (2,200 miles) east of Moscow.
The shopping centre, covering 23,000 sq m (248,000 sq ft), opened in 2013. It includes a petting zoo, all of whose animals are reported to have died.
Yevgeny Dedyukhin, deputy head of the Kemerovo region emergency department, said the area of the fire was about 1,500 sq m.
"The shopping centre is a very complex construction," he said. "There are a lot of combustible materials."