Access to records which, under the Oklahoma Open Records Act, would otherwise be available for public inspection and copying, shall not be denied because a public body or public official is using or has taken possession of such records for investigatory purposes or has placed the records in a litigation or investigation file. However, a law enforcement agency may deny access to a copy of such a record in an investigative file if the record or a true and complete copy thereof is available for public inspection and copying at another public body.