"We're sending people in inhumane conditions and dispersing them across the nation," Long said.

On Tuesday, the federal government began busing 140 migrants for processing in Murrieta every 72 hours, raising concerns about operational capacity, Long said. The initial federal plan called for 500 people, which was lowered to 300, but the city strongly opposed those plans.

"The concern we have is the sustainability of 140 every 72 hours," Long said. "We don't see this stopping any time soon."

Long said earlier this week that his city "continues to object to the transfer of illegal immigrants to the local Border Patrol office." A subsequent protest in agreement became raucous Tuesday; a counterprotester was spat upon. Long described portions of that protest as "unfortunate" and "deplorable."

The city had offered U.S. officials a mobile health clinic to help them provide health screenings and inoculations for the migrants, but the federal approval process would have been too long.

"The world has never been able to see how compassionate our community is because we never got there," Long said.

The first protest

Federal officials weren't disclosing arrival times Friday for the immigrants or even the cities receiving them, citing safety concerns in light of Tuesday's protests in Murrieta. The town became a battleground over immigration that day as angry crowds chanted, "Go back home," and forced buses carrying immigrants to turn around.

Counterprotesters squared off with demonstrators, leading to a shouting match over the nation's immigration system.

As chaos ensued, federal officials rerouted the 140 undocumented immigrants to U.S. processing centers at least 80 miles away, in the San Diego and El Centro areas.

A tide of Central Americans illegally entering the United States has overwhelmed a system already buckling under the weight of the nation's 11 million undocumented immigrants.

Unlike undocumented Mexican migrants, who are often immediately deported, the United States detains and processes Central Americans, who are eventually released and given a month to report to immigration offices.

Protests and tension

Many never show up and join the undocumented population, according to the National Border Patrol Council, the union representing Border Patrol agents.

The immigrants rejected by Murrieta protesters were initially held in Texas, where U.S. facilities are overflowing, forcing detainees to be sent to other states for processing.

The government doesn't have the room to shelter the children with adults: There's only one family immigration detention center, in Pennsylvania. To assist the unaccompanied children, the Obama administration opened shelters last month on three military bases because federal facilities more designed for adults were overrun with minors.

Tuesday's busloads didn't include any unaccompanied minors, said Murrieta Police Chief Sean Hadden. The children on the buses were apparently in the company of relatives or other adults, said an official with the National Border Patrol Council.

Immigration rights advocates denounced the protesters.

"It is deplorable that people espousing anti-immigrant hate language created unnecessary tension and fear for immigrant mothers and their children," said Pedro Rios, a community representative of the San Diego Immigrant Rights Consortium. "Even more concerning is that elected officials in the city of Murrieta instigated this tension. Mothers and their children on these buses have suffered through enough trauma."

Journey from Texas

The U.S. government earlier flew the 140 Central American immigrants from south Texas to San Diego. Federal agents were busing them to Murrieta for processing at the Border Patrol station when the standoff took place Tuesday.

After the buses turned around, the immigrants were taken to a U.S. Border Patrol station in San Diego, said Ron Zermeno of the National Border Patrol Council.

The United States is struggling to accommodate an influx of undocumented immigrants, particularly a wave of unaccompanied children from El Salvador, Guatemala and Honduras. The U.S. government doesn't have enough beds, food or sanitary facilities.

Authorities estimate 60,000 to 80,000 children will cross the border without parents this year in what the White House has called an "immediate humanitarian crisis."