Two people have been killed and an alarming spike in radiation was noted in the northern Russian city of Severodvinsk after a rocket engine exploded at a defense installation, The Guardian reports, citing Russian news agency Tass. The mishap is the second such deadly accident in a week after a military ammunition depot caught fire in Siberia, killing one and forcing 16,500 people to evacuate this week. Russian state media reported the Severodvinsk accident happened aboard a vessel, while the military said it happened on land. Some news reports also stated there was a spike in radiation levels near Nyonoks, which hosts a testing site for ballistic missiles carried on nuclear-powered submarines. Russia’s defense ministry denies any increase in radiation levels, insisting the most recent accident caused “no harmful discharges into the atmosphere.”