Five children were among 10 people killed overnight when a fire broke out in a seven-store apartment building in a suburb of the eastern French city of Lyon, the local government said Friday.

The cause of the fire was still unclear, authorities said, adding that the blaze erupted a little after 3:00 am (0200 GMT) in Vaulx-en-Velin. Fourteen others were injured, one of whom was in serious condition.

Two firefighters suffered light injuries while battling the blaze, which broke out on the ground floor of the building and spread upwards, they said.

Nearly 170 firefighters had been deployed at the building in the northern suburb.