Less than 200 Central Americans, part of a caravan of asylum seekers that traveled through Mexico to the border with San Diego, left a cross-border rally Sunday afternoon, prepared to turn themselves in to U.S. authorities.

Before they could cross the border, however, U.S. Customs and Border Protection (CBP) officials said the border was at capacity for people without appropriate entry documentation.

"Depending upon port circumstances at the time of arrival, those individuals may need to wait in Mexico as CBP officers work to process those already within our facilities," CBP Commissioner Kevin McAleenan said. "As sufficient space and resources become available, CBP officers will be able to take additional individuals into the port for processing. CBP will communicate with Mexican authorities for operational awareness on this issue of capacity within CBP facilities as appropriate."

Late Sunday afternoon, however, 50 people were allowed into the San Ysidro Port of Entry. They are still on the Mexico side of the facility and have not entered the U.S. side for processing, according to CBP officials.

Another 50 migrants have been camping outside the facility a little farther away.

BREAKING: Supporters of Migrant Caravan preparing to cross #USmexico border to seek asylum climb to the top of border fence. Stay w #NBC7 & @TLMD20 for complete coverage. Watch LIVE @ https://t.co/Zn9YGkme6g pic.twitter.com/E3IfuxiFWK — Liberty Zabala (@LibertyNBC7SD) April 29, 2018

The migrants, who traveled in five old school buses, ate lunch Sunday before making a roughly 15-minute walk to San Diego's San Ysidro border crossing, the nation's busiest. Many are fleeing violence in their home countries and will ask the U.S. for asylum.

They reached the border last Tuesday and have been sleeping in tents and attending legal seminars given by volunteer attorneys.

Supporters of the #MigrantCaravan are marching from Balboa Park to Chicano Park, then to the border on Sunday pic.twitter.com/9a4nu45QX1 — Ramon Galindo (@RamonGalindoNBC) April 28, 2018

Secretary of Homeland Security Kirstjen M. Nielsen warned in a statement Sunday that anyone — including people advising the migrants — caught breaking U.S. immigration laws would be prosecuted.

"Let me be clear: we will enforce the immigration laws as set forth by Congress. If you enter our country illegally, you have broken the law and will be referred for prosecution. If you make a false immigration claim, you have broken the law and will be referred for prosecution. If you assist or coach an individual in making a false immigration claim, you have broken the law and will be referred for prosecution."

She also requested that Congress work with her "to quickly pass legislation to close the legal loopholes that prevent us from securing our borders and protecting Americans."

[NATL-LA GALLERY] Scenes From the Border: Asylum Seekers Wait Their Turns in Tijuana

The migrants' arrival marked the end of a monthlong journey by foot, freight train and bus. Many traveled with their families and on Sunday morning, four couples in the group were married in a ceremony at the border. Meanwhile, some supporters climbed the wall separating San Diego and Tijuana on Sunday to wave signs under the watchful eyes of U.S. Border Patrol agents.

There were hundreds of people in Playas Tijuana to support #MigrantCaravan including some people who climbed the border fence. There were several @CBPSanDiego agents watching the crowd pic.twitter.com/sgy5Zs9L04 — Ramon Galindo (@RamonGalindoNBC) April 29, 2018

President Donald Trump has called the caravan dangerous and tweeted last week that he has issued orders to "not to let these large Caravans of people into our Country." Trump and members of his Cabinet have been tracking the caravan, calling it a threat to the U.S. since it started March 25 in the Mexican city of Tapachula, near the Guatemala border. They have promised a stern, swift response.

On the U.S. side of the border, dozens of people marched to Border Field State Park to greet the families.

Claudia Treminio came to the United States when she was 12 to escape the violence in El Salvador.

"I connect with them in that way, the way that I've gone through that journey that they embarked on," she said. "I'm happy to see that they are here. They're safe, I'm also saddened to see them on the other side and still see them fighting for their dreams.”

Several Border Patrol agents were at the park to keep an eye on the crowd.

Caravans such as these are a common method to bring attention to asylum seekers. This one has garnered more attention because Trump used the caravan as a justification for the border wall.

Attorney General Jeff Sessions called the caravan "a deliberate attempt to undermine our laws and overwhelm our system" and said he may assign additional judges to handle cases involving the caravan.

Many Central American asylum seekers say they face death threats by criminal gangs in their homelands.

A group of demonstrators marched from Balboa Park to Chicano Park in San Diego on Saturday to show solidarity with the migrants, who are fleeing violence in Central America.

"The President wants to send the Guard to the border, however, this is not an invasion," said Treminio, who now lives in the Los Angeles area. "I am here to welcome them with love."

U.S. immigration lawyers are telling the asylum-seekers that they face possible separation from their children and detention for many months. They say they want to prepare them for the worst possible outcome.

"We are the bearers of horrible news," Los Angeles-based lawyer Nora Phillips said during a break from legal workshops for the migrants at three Tijuana locations where about 20 lawyers gave free information and advice. "That's what good attorneys are for."

Any asylum seekers making false claims to U.S. authorities could be prosecuted as could anyone who assists or coaches immigrants on making false claims, Nielsen said. Administration officials and their allies claim asylum fraud is growing and that many who seek it are coached on how to do so.

Asylum-seekers are typically held up to three days at the border and then turned over to U.S. Immigration and Customs Enforcement. If they pass an asylum officer's initial screening, they may be detained or released into the U.S. with ankle monitors.



The San Ysidro crossing, which admits about 75,000 people a day into the country, may be unable to take asylum-seekers if it faces too many at once, forcing people to wait in Mexico until it has more room, according to Pete Flores, U.S. Customs and Border Protection's San Diego field office director. Flores said earlier this month that the port can hold about 300 people temporarily.

The Border Patrol said, "several groups" of people in the caravan have entered the country illegally since Friday by climbing a dilapidated metal fence. It didn't say how many.

Since Congress failed to agree on a broad immigration package in February, administration officials have made it a legislative priority to end what they call "legal loopholes" and "catch-and-release" policies that allow asylum-seekers to be released from custody while their claims wind through the courts in cases that can last for a year.

The lawyers who went to Tijuana denied coaching any of the roughly 400 people in the caravan who recently arrived in Tijuana, camping out in shelters near some of the city's seedier bars and bordellos.

Some migrants received one-on-one counseling to assess the merits of their cases and groups of the migrants with their children playing nearby were told how asylum works in the U.S.