Since the end of June there have been 15 strong-arm and armed robberies in Palo Alto, Agent Dan Ryan said. Four have occurred in just in the last week.
"It may not seem like a lot, 15 robberies in three months, but it's a lot for us," Ryan said.
In the past week, three women had their purses snatched from them while they were walking home and a janitor was mugged as he walked between buildings near the business district.
"Year after year, the average number of robberies is the same" and the recent trend marks a distinct increase, Ryan said.
Extra patrol units will be dispatched to the affected areas, and police are warning residents to be alert and aware of their surroundings.
The robberies are not occurring in one particular area, but throughout the entire city, Ryan said.
Anyone with information on the crimes is asked to contact Palo Alto police at (650) 329-2413.