MURRIETA, Calif. -- Rumours had swirled among anti-immigration activists near a U.S. Border Patrol station in Southern California that the agency would try again to bus in some of the immigrants who have flooded across the U.S.-Mexico border.

By Friday afternoon, dueling anti- and pro-immigration rallies had assembled.

People in the crowd of 200 outside the station in Murrieta waved signs and sometimes shouted at each other. One banner read: "Proud LEGAL American. It doesn't work any other way." Another countered: "Against illegal immigration? Great! Go back to Europe!"

It was not certain, however, that any buses would arrive on Friday. Because of security concerns, federal authorities have said, they will not publicize immigrant transfers among border patrol facilities. By late afternoon, many demonstrators were leaving.

The city has become the latest flashpoint in the intensifying immigration debate when a crowd of protesters waving U.S. flags blocked buses carrying women and children who were flown from overwhelmed Texas facilities amid an influx of immigrants.

In recent months, thousands of children and families have fled violence, murders and extortion from criminal gangs in Guatemala, El Salvador and Honduras. Since October, more than 52,000 unaccompanied children have been detained.

The crunch on the border in Texas prompted U.S. authorities to fly immigrant families to other Texas cities and to Southern California for processing.

Federal authorities had hoped to process some at the station in Murrieta, about 55 miles (90 kilometres) north of downtown San Diego.

"This is a way of making our voices heard," said Steve Prime, a nearby resident. "The government's main job is to secure our borders and protect us -- and they're doing neither."

Immigration supporters said the immigrants need to be treated as humans and that migrating to survive is not a crime.

"We're celebrating the 4th of July and what a melting pot America is," said resident Raquel Alvarado.

The city's mayor, Alan Long, became a hero to those seeking stronger immigration policies with his criticism of the federal government's efforts to handle the influx of thousands of immigrants, many of them mothers and children.

However, city officials tried to clarify Long's comments, saying he was only asserting that the local Border Patrol station was not an appropriate location to process the migrants.

The statement Thursday by City Manager Rick Dudley, suggesting that protesters had come from elsewhere in Southern California, expressed regret that the busloads of women and children had been forced to turn around.

"It made this extremely compassionate community look heartless and uncaring. That is NOT the Murrieta that we all know and love," he wrote.

Long said by telephone Friday that forcing the buses to turn around was neither planned nor called for. "It's not reflective of our city. This controversial topic has turned us upside down," Long said. "It just happened to land on our doorstep, and we want to be part of a solution."

The Border Patrol is coping with excess capacity across the Southwest, and cities' responses to the arriving immigrants have ranged from welcoming to indifferent.

In Nogales, Arizona, the mayor has said he welcomes the hundreds of children who are being dropped off daily at a large Border Patrol warehouse. Residents have donated clothing and other items for them.

In New Mexico, however, residents have been less enthusiastic.

At a town hall meeting this week, residents in Artesia spoke out against a detention centre that recently started housing immigrants. They said they were afraid the immigrants would take jobs and resources from U.S. citizens.