Story highlights A top Hillary Clinton aide traveled to New York in 2012 to help the Clinton Foundation in a job search

It's the latest instance of overlapping interests between the State Department and the Clinton Foundation

(CNN) A top aide to Hillary Clinton at the State Department traveled to New York to interview job candidates for a top job at the Clinton Foundation, a CNN investigation has found.

The fact that the aide, Cheryl Mills, was taking part in such a high level task for the Clinton foundation while also working as chief of staff for the secretary of state raises new questions about the blurred lines that have dogged the Clintons in recent years.

Upon entering office as secretary of state, Hillary Clinton and the Clinton Foundation agreed to a set of rules to ensure any activities by the foundation would not "create conflicts or the appearance of conflicts for Senator Clinton as Secretary of State."

On June 19, 2012, Mills, then the chief of staff for Clinton at the State Department, boarded a New York City-bound Amtrak train in Washington's Union station.

The next morning, at the offices of a New York based executive search firm, Mills would interview two high-level business executives. Her mission was to help the Clinton Foundation find a new leader, a source told CNN.

Read More