The alleged robbery took place in the 600 block of Highland Avenue at the Las Torres Mexican restaurant at around 8:15 a.m.
Police said they got a 911 call from an employee at the restaurant shortly after 8 a.m. The woman said she had been just been robbed by a man inside the business. Responding officers eventually summoned a SWAT team to the scene, and its members took up positions outside the business while officers attempted to contact the woman inside the restaurant.
They were unable to communicate with her until noon, when she finally called them back.
"She was in the back ... locked herself in a storage room," said Sgt. Jose Tellez of the National City Police Department. "We suggested for her to stay inside and not come out, because we were still trying to determine if there was any type of movement inside the restaurant."
She fled the restaurant around 12:30 p.m., however.
A few minutes after she ran past police lines, SWAT teams wearing body armor fired a flash-bang grenade into the restaurant and entered the premises after it detonated.
Officials said their search failed to yield a suspect. Detectives are investigating the alleged robbery. They do not have a detailed description of the suspect, but they did say he might be armed.
During the standoff, authorities evacuated nearby business and homes, and Highland Avenue was closed to traffic between 4th and 8th streets.