Acceptance Letter Discrepancy?

A week ago, I recieved an email with a link to the admissions that I was accepted into UCSD, in my first-choice Warren college, but as an Undeclared. However, I just recieved the acceptance letter giving me a certificate of admission and a letter that stated I was officially accepted into Mechanical Engineering instead. I sent an email to the Admissions office, but, guys, which one do you think is likely more valid?