It happened around 11:30 pm on Thursday at the Sinclair station on Blackstone and Dakota Avenues.
When officers arrived, they found multiple shell casings in the parking lot and the street.
Detectives say they have not received any reports of shooting victims. There were no witnesses at the scene.
Investigators say surveillance video will help them identify the shooters.
"Based on the video, it does appear that there was an exchange of gunfire. We're probably going to have to analyze the video a little bit more. But based on what we have right now, it appears that two groups of people were firing back and forth," said Fresno Police Lt. Israel Reyes.
Detectives say they have not received any reports of shooting victims.
Police are looking for a red, four-door vehicle and a gray Chevy Malibu, which gunfire may have hit.
Anyone with information is asked to call Fresno Police Department.