At least 16 people were killed Saturday morning when a fire broke out at a warehouse in an industrial area north of Moscow, authorities said. Firefighters only discovered the bodies after the fire had been contained. "When the fire was being put out, a room that had been cut off by the flames was discovered," Russia's TASS news agency quoted the emergency ministry's press service as saying. "Firefighters tore down the wall and found 16 dead." The fire erupted at around 5 a.m. Saturday morning and was put out at around 7 a.m. The victims are believed to be migrant workers from former Soviet republics who had been working at a printing company that owned the warehouse. The cause of the fire remains unknown, but Mayor Sergei Sobyanin promised that authorities would open an investigation into the incident.