The incident happened at about 1 p.m. Wednesday when the suspect, a U.S. citizen, crossed the border on foot and approached Customs and Border Protection inspection booths, the U-T San Diego reported.
The suspect then threw the gasoline bomb in the direction of the inspection booth in lane 23 near four CBP officers and motorists, said CBP spokeswoman Angelica De Cima.
No one was injured in the incident, and the blast didn't cause any damage, De Cima said.
CBP officers put out the flames with a fire extinguisher.
The suspect was arrested at the scene and booked into the Metropolitan Correctional Center.