MOSCOW -- Criminal negligence is suspected in a chemical plant explosion in a Russian city in eastern Siberia Tuesday that killed at least four people.
The blast happened around 5:30 a.m. at the Sayanskkhimplast factory in the city of Sayansk, the Novosti news agency reported.
Four other employees were injured, emergency officials said.
The plant manufactures 250,000 tons of polyvinyl chloride each year, and uses the toxic chemical dichloroethane in the process.
Investigators told Itar-Tass it appeared a build-up of fumes led to the blast.
There was a fire that was quickly extinguished, and officials said there was no major environmental threat, the report said.
Prosecutors told the news agency a criminal investigation was launched immediately on suspicion of negligence under labor law.
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