(CNN) - Five employees of Russia's atomic agency have been killed in a blast at a military test site in northern Russia, the state-run Rosatom said Saturday. The five were killed "while testing a liquid jet propulsion system," Rosatom, which oversees all Russian nuclear projects, said in a statement on its website. The Russian Defense Ministry said at the time that two people died while testing the liquid jet propulsion system and that no dangerous substances were released into the atmosphere. "The tragedy occurred during works related to the engineering and technical support of isotopic sources in a liquid propulsion system," the ministry said in a statement. However, local authorities in Severodvinsk released a statement Thursday that said there was a radiation spike following the blast.

iStock/BWBImages(CNN) - Authorities in northern Russia detected a brief rise in radiation levels following a deadly explosion at a military training ground in the Arkhangelsk region, state news agency TASS reported Thursday. "The brief rise of the radiation level was registered in Severodvinsk at about noon," said Kseniya Yudina, a spokeswoman for the city, TASS reported. The Arkhangelsk regional governor told TASS that the area around the explosion would not be evacuated. State news agency RIA-Novosti, citing regional law enforcement, put the casualty toll higher, saying two people died and 15 were injured in the explosion. The agency told RIA-Novosti the incident occurred 30 kilometers from the city of Severodvinsk, and that circumstances were being clarified.