Correct usage of word "reason" with "twofold"

I want to say that there were two reasons for something. Which would be grammatically correct?

"The reason for this is twofold" or "The reasons for this are twofold"

Or is it that both of these are technically correct but mean separate things? Do they both mean the same thing but one is preferred over the other?

Thanks for you help

How about: "The reason is twofold." By saying that the reason is twofold, it means that there are two parts to the same reason, not that there are two separate reasons. If you wanted to say that there are two separate reasons for a phenomenon, then I would simply say: "There are two reasons for this occurrence," or something along those lines.