Even during a comparatively smooth performance, Amy Winehouse managed to stir up some controversy, even during a relatively smooth set, Saturday night at the Glastonbury Festival in England.

Performing her signature hit "Rehab" while walking along the front row of the audience, Winehouse appeared to punch an unseen fan, judging by a video posted on the BBC News Web site. As she continues singing, Winehouse can be heard grunting as she thrusts a fist into the crowd, then quickly scampers backwards on her high heels under the watch of several large security guards. On continuing her forward progress, she appeared to glare at the person in the spot where the incident took place.

According to the BBC, police said they had received no complaints of assault following the show, and festival organizers said there would be no investigation into the incident.