The blast occurred on Monday when a repair crew was dismantling a pipeline at a workshop in the Avangard site in the city of Sterlitamak, Bashkortostan, around 900 miles east of Moscow, Russian news outlet RBC reported.
The site belongs to the state corporation Rostec and produces parts for multiple launch rocket systems. The company has been sanctioned by the European Union, Switzerland and Ukraine.
The company said that the cause of the incident is being established. Russia's Investigative Committee said workers may have violated safety guidelines when cutting the pipes.
The committee said in a statement that a criminal case has been initiated into "the violation of the requirements of industrial safety of hazardous production facilities, resulting in the death of two or more persons by negligence." Newsweek has contacted Rostec and the investigative committee for comment.
While there is no evidence of any outside cause for the explosion, the incident is the latest to hit a Russian military facility in recent months.
Comment: And it's for that reason that one would suppose that, whilst it may have been a breach of safety procedure, it seems more likely that this was sabotage. Because these 'unusual' fires and explosions, across all areas of Russian industry, as well as at other places like training facilities and malls, began occurring at least at the start of the SMO, if not before. Wikipedia even has a page listing many of them: Russian mystery fires (2022-present)
Ukrainian Defense Ministry's Main Intelligence Directorate (GUR) said on Monday that at least one Russian warplane as well as ammunition storage facilities were destroyed in a strike at the Morozovsk air base in the Rostov region on Saturday.
The GUR said satellite imagery showed that a Sukhoi Su-34 fighter bomber had been destroyed and two others likely damaged in the attack.
In April, Ukraine said it had struck the same airfield in a drone strike that destroyed at least six Russian military aircraft.
Last month, a fire broke out at the military factory Uraltransmash in Yekaterinburg, Russia, which produces self-propelled artillery howitzers such as the Msta-S and Tulip. The blaze followed at least three explosions, after which thick smoke was seen billowing into the air.
Often without directly claiming responsibility, Ukraine has stepped up attacks inside Russian territory on targets linked to Moscow's full-scale invasion.
Comment: As other incidents suggest - including the mall terrorist attack to the German military plot to bomb the Crimean bridge - it's likely that the Kiev-junta can't claim all the credit: US, UK and Ukraine could be behind Moscow terror attack - FSB chief
In April, a Ukrainian drone struck Russia's third-largest oil refinery in Tatarstan, according to a Kyiv intelligence source. Also in April and in the same region, Ukrainian drones hit the Gorbunov Aviation Plant, which makes missile carriers and aircraft such as Tu-22M3 and Tu-160M bombers.
Meanwhile, Russian attacks targeted at least 11 Ukrainian regions overnight Monday, killing at least three people and injuring at least 19, according to local authorities.
Ukraine's Air Force said that Russia had launched 16 Shahed-type drones from Cape Chauda in occupied Crimea and the Russian city of Kursk.
Russia also launched four Iskander M/KN-23 ballistic missiles from the Voronezh Oblast and two Kh-59 guided missiles from the Azov Sea, Ukraine said.
Comment: The fire that occurred today: Notably the sabotage against Russia is occurring alongside a surge of similar incidents in the West - although largely against the food supply chain - and it seems probable that those responsible may be linked: