Answer:
It depends on the school and their preferred approach to the field. However, in most all cases that I know of, a degree in any of the engineering fields is a bachelor in sciences degree (BS).
To expand a bit on that part about "it depends on the school": At some schools there's an actual distinction between the degrees. For example, at my undergraduate school, a BA required 12 credits in a single foreign language, while the BS did not (there were a few other minor differences depending on the major as well). However, at a different school I attended, there was absolutely no difference in the program of study and students were simply asked on the form they filled out just before graduation which of the two they would prefer to have printed on their diploma. (Most of the science and engineering students opted for "Science": "That bridge is unstable!" "Yes, but it certainly is pretty, isn't it?")