Russia's meteorological authorities have disclosed that up to 16 times the normal radiation levels were observed around the site of an August 8 explosion at a Russian military facility.
The deadly blast occurred in the northwestern region of Arkhangelsk.
The authorities say radiation levels rose from four to 16 times above normal levels at six of eight observation posts around the blast site, following the incident. They also report the highest measurement was 1.78 microsieverts per hour.
State-run Tass news agency quoted a senior Severodvinsk City official as saying radiation levels rose to 2 microsieverts per hour for about 30 minutes in the city. That's about three times the permissible level.
US President Donald Trump indicated that the explosion was caused by a failed test related to a nuclear-powered cruise missile.
Russia is working hard to develop cutting-edge weapons in rivalry with the US.
The Russian government has not yet disclosed details of the incident.