Police spokesman Markus Sicius said an explosion of two gas tanks early Saturday in Harthausen near Ludwigshafen led to the evacuation of some 3,000 residents after the firefighters were injured.
The fire on the grounds of a gas company was first reported at 4:20 a.m., and while firefighters were trying to douse the flames, the fire spread to two trucks with gas tanks which exploded.
Sicius said one of the injured was in a critical, but not life-threatening, condition.
Residents were taken to nearby Dudenhofen and put up at a town hall.
He said the cause of the fire was not immediately known.