The Secret Service is denying that it conducted a security sweep of the Michigan home belonging to the sister of former Massachusetts Gov. Mitt Romney (R).

Roll Call earlier reported that the sweep took place, suggesting that it might be an indication that Romney was in line to be selected as Sen. John McCain’s (R-Ariz.) vice presidential running mate.

“The Secret Service did not conduct any advance, sweep or security assessment at the residence of former Governor Romney’s sister, as referenced in [the] Roll Call article. We have no knowledge of any security sweep taking place,” read a statement from the Secret Service.

Sources with strong Michigan ties earlier told Roll Call that the Secret Service conducted a sweep of the home of Romney’s sister. Romney was raised in Michigan, where his father served as governor.

However, one campaign operative familiar with the workings of a presidential-level campaign cautioned that a sweep of such a location could have been conducted in advance of Romney appearing as a surrogate — not the vice presidential nominee — at an upcoming McCain campaign stop in Michigan.

Any McCain campaign appearance in Michigan would likely include Romney, who remains popular there.

Other sources and some news reports have also suggested that Romney in the last few days might be traveling with a security detail, although exactly who employs this security detail could not be confirmed.

Romney finished first in Michigan’s January GOP presidential primary. McCain finished second in that race.