SAN DIEGO (FOX 5/KUSI) -- Detectives are investigating a series of burglaries in northern San Diego communities, where at least five businesses have been hit over the past week. The incidents occurred within a few miles of each other, raising concerns of a possible serial burglar. Surveillance footage from Ponce’s Mexican Restaurant in 4S Ranch shows a burglar smashing a glass door with a sledgehammer at around 3:40 a.m. on Friday. The owner reported that the thief grabbed several bags filled with an undisclosed amount of money from a back office before leaving the scene. Tijuana police offer to inspect vehicles at border to expedite crossing times Just 30 minutes earlier, Mostra Coffee, located a few blocks away, was also targeted. Co-founder Jelynn Malone said a burglar ransacked the store, opening every cabinet and dumping out items. “Breaking into multiple locations in one shopping center… these alarms are going off,” Malone said. “You just feel targeted, and it’s really, really sad that people would take advantage of others this way.” Malone added that the same burglar is believed to have also broken into a Jamba Juice nearby, smashing the glass door there as well. It remains unclear if the same individual is responsible for burglaries at Yogurt Heaven and Santana’s Restaurant on Scripps Poway Parkway last week, but employees confirmed that surveillance footage shows a thief using a sledgehammer to break into those businesses as well. Police investigate shootout at Linda Vista gas station For Malone, the crime is not only financially damaging but also disheartening. “It’s a lot of work to run a business… I know other small business owners are feeling the same way,” she said. The burglar took a cash register containing a few hundred dollars from Mostra Coffee. As the holiday season approaches, Malone is urging other small business owners to be cautious. “Do not leave any cash in your store. Make sure all your security cameras, security alarms are working properly, and don’t leave anything in plain sight that can be stolen,” she advised. San Diego police detectives are investigating the burglaries, but say it's not known at this time if they are connected. Anyone with information is encouraged to contact detectives.