At least 28 000 people were evacuated from their homes on Friday as fires raged around a military weapons depot in Russia.
Tonnes of artillery shells and rockets are stored at the base near the town of Izhevsk, 1,200 kilometres east of Moscow.
Fifty-two people are reported injured.
The explosion comes a week after a similar blast at a base in neighbouring Bachkortostan.
Deputy Defence Minister Dmitri Bulgakov tried to calm fears, saying the missile warheads have not exploded.
There are 10,000 to 150,000 tonnes of ordnance at the site, according to press reports.
The fire broke out yesterday evening. Russian authorities say the situation is now under control.