Two military officers were killed in an explosion when cleaning a propellant storage tank at cosmodrome Plesetsk, northern Russia.
Although the tragedy took place on 9 November, Russian authorities have only announced the accident yesterday.
A statement released by Russia’s ministry of defence said three other servicemen were hospitalised after inhaling toxic nitrogen tetroxide vapours but their condition was said to be stable.
The accident took place after engineers at Plesetsk, some 500 miles north from Moscow, commenced with preparations for the launch of the SWARM mission of the European Space Agency (ESA) scheduled for 22 November. However, the explosion was said to be unrelated to the work conducted ahead of the planned launch of the magnetic field probe, which should be lifted to Earth’s orbit aboard a Rockot launch vehicle.
According to Rene Pischel, head of ESA's permanent mission in Russia, the launch of Swarm, for now, remains set for 22 November.
A criminal investigation will hopefully shed more light on the causes of the blast, which, according to available information, took place as two officers entered a propellant tank on a rail car coming to help another soldier who reportedly lost consciousness after inhaling toxic fumes.
Russia’s Defence Ministry said the soldier who initially lost consciousness ignored safety regulations.
Last week’s tragedy is the first known fatal accident involving work at the space base since a 2002 Soyuz crash killed a soldier.
The military-operated Plesetsk Cosmodrome is a secondary facility as Russia conducts most of its missions from the Baikonur Cosmodrome leased from the government of Kazakhstan.