Livermore police are warning female joggers or walkers to be aware of a man who approaches women and pulls down their pants.
There have been six reports of an unknown man with dark hair who approaches female joggers from behind on Patterson Pass Road and Holmes Street and pulls down their pants before running away, police said.
The suspicious activity has happened at an inconsistent frequency on various days of the week and at different times, police said.
In most cases, the women have been listening to digital music players and do not anticipate the man's advances, according to police.
The Livermore Police Department encourages runners or walkers to be aware of their surroundings when exercising. They recommend that women take advantage of the "buddy system" to avoid walking or running alone.
Police also suggest breaking a workout routine because they are not sure whether the man has been watching for patterns.
Joggers are also advised to increase their awareness when wearing music players with earphones, as these devices can be distracting, police said.
Officers said they do not have a more detailed description of the suspect because he surprises the victims and darts away.
Anyone with additional information is asked to call Livermore police at (925) 371-4733 or (925) 371-4762.