At least 12 people, including three children, perished in a fire in a Moscow factory that caused the roof to collapse, Russian authorities said on Sunday.

Investigators said the blaze engulfed an area covering 3,000 square metres (over 32,000 square feet) in a factory situated in the east of the Russian capital, which makes clothing according to local media.

‘Twelve bodies were recovered’ at the site, emergency ministry spokeswoman Oksana Zolotova told TASS news agency.

Authorities said the victims of the fire were likely migrants who worked and lived at the factory.

Russia's child rights commissioner, Pavel Astakhov, wrote on Twitter that three children had died in the blaze.

‘Three children were killed, one of whom was a baby,’ Astakhov wrote.

‘Preliminary evidence suggests that migrants lived at their workplace, some even with their children.’

The fire broke out at around 1800 GMT on Saturday and was only extinguished around five hours later, authorities said.

The cause of the blaze remains unknown. A criminal investigation was launched to determine whether it may have erupted due to negligence or arson.

The emergency situations ministry initially reported that there had been no fatalities in the fire, but investigators later said that bodies had been found at the site.