Metro riders glued to smartphones beware: There’s been an uptick in “snatch and grab” crimes on the system lately, enough so that the Metro Transit Police Department held a press conference today to address it.

According to MTPD chief Ron Palvik (via Twitter), there was a 48 percent increase in this type of crime during a recent two-week period. That translates into 40 devices being stolen in 14 days. The advice provided by Palvik is pretty straightforward: Be aware of your surroundings, keep two hands on your fancy device, don’t use them near doors or escalators, and set up a GPS system so devices can be tracked.

MPTD also released security footage showing a “snatch and grab” at the Capitol Heights Metro station in late July to illustrate how easy it can be to lose your treasured electronics. In the video, the victim chases after the thief, which is not recommended by MPTD.

Palvik advised at the press conference, “Do not chase, instead become a good witness.”