When you applied for the "new" job, you most probably signed papers allowing the BI of the "new" job to obtain information concerning your medical, financial, legal, and any other record that is available about you.  The only limitation is how far the BI wants to go and what is available and still on record.  Almost certainly, all security files and investigations will be available unless they are sealed by a "higher authority" such as the Department of Defense "Black OPS" or deemed a national security risks by an authority with more jurisdiction (higher in the government henpecking order) then the investigating authority or BI.

In short, you have to know that anything that you have done in your life past 18 is fair game for a BI.  The only question is, "Is it available in a record somewhere?"

Sorry if this complicates things for you.

I currently work for a federal law enforcement agency and I am applying to another fed agency.  My question is when the background is done prior to employment does the investigator have access to the paperwork you filled out to get your present job.  That is, when I hired on with my current agency and when I joined the Military I answered questions in writing on my drug use history.  Will the BI have access to these records?