More than 100 people pelted
Nobody was seriously injured and it's not clear whether the crowd was trying to enter the U.S. illegally or hold a demonstration, but the sight of a large crowd surging beyond the border rattled nerves.
Agents said it harked to the days in the 1990s when migrants would run across the border en masse, in so-called banzai runs that would overwhelm agents. As the crowd on Sunday crossed the Tijuana River into California, more than one dozen agents responded to the border fence atop the levee and deployed pepper spray to hold them back, triggering the melee.
Several agents were hit in the arms and legs with rocks and one agent was hit in the head with a filled water bottle, officials said. The crowd eventually dispersed.
"It was extremely unusual," said agent Timothy Hamill, an agency spokesman. "It was dangerous, very dangerous."
Demonstrations along the border are not uncommon and protesters have at times briefly crossed the border in symbolic displays of defiance. The confrontation Sunday occurred along one of the most heavily fortified spots on the border just west of the San Ysidro port of entry. There were no arrests.
"While attacks on Border Patrol agents are not uncommon, the agents showed great restraint when faced with the dangers of this unusually large group," said Paul Beeson, the chief patrol agent for the agency's San Diego sector.