EXCLUSIVE: Federal prosecutors have pursued a “massive” investigation of off-label marketing of drugs at GlaxoSmithKline Plc, and the indictment (pdf) of a former associate general counsel is “just a small piece of it,” according to one of her defense attorneys.

The attorney, Reid Weingarten of Steptoe & Johnson, said the Glaxo probe includes nearly 200 witnesses and almost 100 grand jury transcripts. And prosecutors said new information is still coming in.