Three of the four victims killed in the explosion at the Avangard plant in Gatchina, near St. Petersburg, were foreigners, a source from emergency services told TASS on Saturday.

"Three killed people were foreigners," he said, adding that the victims had been identified.

Earlier reports said that one of the victims was a national of Belarus.

An explosion rocked the Avangrad plant of pyrotechnical devices and lawn furniture in the town of Gatchina, Leningrad region, on Friday afternoon. Four died in the explosion, while seven more were injured, including an underage girl.

By now, the rescue teams have finished digging through rubble. Experts are examining flats and houses nearby to document damage from the explosion,

A criminal case was opened on charges of safety rules violations leading to two or more human deaths through negligence. The plant’s chief engineer has been detained.