The deceased were working in a greenhouse facility in Nesterovo village, Ramensky district.
18 Vietnamese workers work at the facility, Vietnam News Agency cited the Vietnamese Embassy in Russia as saying. The number of workers at the facility at the point of the fire has not been confirmed.
The embassy said it is taking steps to verify the victims' identities.
Apart from the eight deceased, another worker was severely burned and has been hospitalized. The injured is a Vietnamese woman from the northern Phu Tho Province, who suffered burns all over her body as well as respiratory burns, said Vietnamese Embassy in Russia.
"Eight bodies were found in the fire. They might be Vietnamese," said Anatoly Suprunovsky, acting deputy minister of the Russian Ministry of Emergency Situations, as cited by AFP.
The ministry said the fire was possibly caused by an electrical fault.