Three men were probably burned to death on Saturday at the eastern Athens suburb of Vyronas, inside a motorcycle repair shop.
The fire at the basement of the building had the three men, aged between 30 and 35 years, trapped as the entrance was locked.
Neighbors said they also heard explosions from the building.
Fire fighters estimate that the men could not get out as the only exit was through a narrow staircase. They likely fainted from the smoke before the flames caught up with them.
The fire service has not yet established the cause of the fire.