Retraction Watch reports on a study by Donald Kornfeld, published last month in Academic Medicine where Kornfeld reviewed 146 US Office of Research integrity (ORI) cases from 1992 to 2003. He found that approximately "1/3 of the accused were support staff, 1/3 postdoctoral fellows and graduate students, and 1/3 faculty. Accusations of fabrication represented 45% of the offenses, falsification 66%, and plagiarism 12%". Read more here.
You can also read COPE's guidelines on Cooperation between research institutions and journals on research integrity cases: guidance from the Committee on Publication Ethics (COPE)