The local emergencies ministry told AFP that search efforts were still going on.
Twelve people were still missing Thursday after a huge explosion tore through a warehouse in the Russian city of Sergiyev Posad, officials said.
At least one person was killed in Wednesday's blast, which investigators said began in a warehouse used to store pyrotechnics.
"There are 12 missing persons reported," the city's administration said in a post on social media.
Officials in the city, which lies 35 miles (56 kilometres) northeast of Moscow, said search and rescue efforts were ongoing.
Rescue workers could be seen sawing through the ruins of a collapsed building overnight, while firefighters sprayed water on the smouldering wreckage.
The cause of the incident was not immediately clear.
Investigators said they had detained the technical director of a pyrotechnics company and opened a criminal case into violations of industrial safety.
Accidental fires are common in Russia, where hundreds of blazes are recorded each year due to ageing infrastructure and poorly enforced safety standards.
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