The answer is yes, but it is better left to a pro.  You need to displace the fumes to weld safely (either by water or inert gas -- water not an option since you will be cutting off a whole end).  The fumes are what explode (you can actually weld on a tank that is full of fuel, so long as there are no fumes __ BUT DO NOT DO IT cause you will never be able to displace all the fumes).    Also, the metal will have "soaked" up a certain amount of gas, so even with all precautions and no matter how long the tank is aired out, you will get "pops" or mini explosions as you weld.  They are loud and scary.  All in all, this is one that is better left to someone who knows what they are doing.