Suppose for a moment these were the real mccoy smugglers. Would you advise starting the search with the statement "We suspect you of smuggling, and we are going to look for drugs", or the non-confrontational "We would like to perform a safety inspection".
These LE guys would like to see noone get hurt, including themselves.
At 10:30 pm that excuse does not wash. It immediately invites disbelief, derision and hostility.