Six people were killed and two injured in a blast at an explosives factory in the city of Chapayevsk in central Russia, according to emergency services sources cited by the state news agency TASS.
The factory, about 30 km (20 miles) southwest of the Volga city of Samara, is operated by Promsintez, one of the main manufacturers of industrial explosives in Russia and the former Soviet Union.
TASS said the explosion had occurred as pipework was being dismantled, and that there had not been a fire.
Alexander Khinstein, a member of parliament for the Samara region, said the blast appeared to have been caused by welding, and might have been the result of explosive remains being left in the pipes.
Since Russia invaded Ukraine early last year, there have been numerous blasts or fires at fuel depots, factories, railway lines and other infrastructure inside Russia.
Authorities have attributed some of them to Ukraine and others to pro-Ukrainian saboteurs. Ukraine hardly ever comments on such incidents, occasionally suggesting that they are the result of internal unrest.
On June 20, five people were killed in an explosion and fire at a gunpowder factory in Russia's Tambov region, but the regional governor ruled out any possibility of an attack or sabotage.
