Mitt Romney's presidential campaign requested "several" years of tax returns from potential vice presidential picks, senior adviser Beth Myers, who ran the search, told reporters Saturday.

Myers said vetting documents were stored in safes in a secure room at campaign headquarters for review by attorneys.

Asked what was inside the safes, Myers replied "tax documents, everything we used.”

And how many years? "Several" she said, declining to provide a more specific number.

Romney has found himself in on defense on the issue. His father, former Michigan Governor George Romney, began the voluntary practice of financial transparency when he volunteered to turn over, in his case, 12 years of tax returns to an inquisitive reporter in 1967. Mitt Romney reportedly provided 23 years of returns to John McCain's vetters when he was up for the vice presidential nomination four years ago. He has said he fears that the Obama campaign and the media will distort the contents of any other returns he might release.