TIJUANA, Mexico — Between two busy highways, four rows of colorful tents have sprung up in a park to house the overflow of migrants who have spilled out of shelters and onto the streets.

The Mexican government and local organizations opened several makeshift shelters in Tijuana this week for the first wave of migrants arriving from Central America with the intention of trying to seek asylum in the United States.

More than 3,000 migrants, who made their way to this border city mostly on foot, are spread throughout Tijuana, according to Mexican authorities. Another 7,000 are not far behind.

The tents in Mapa Park were given to families by organizers from a nearby shelter, Juventud 2000, after it reached capacity and they had nowhere else to send people because all the other shelters also were full.

Down the street, authorities opened Benito Juarez Sports Center to the migrants, who are camping on the baseball field and a concrete playground. Families have set up tents on any spare patch of land they can find.

People watch a fireworks display in July through the U.S.-Mexico border wall in Tijuana, Mexico. David Maung / EPA file

But the tents quickly ran out. Now families are using branches, garbage bags and donated clothes to build makeshift shelters — anything to keep them from being exposed to the elements.

“It’s too cold here,” one little boy said Saturday while rummaging through a pile of donated clothes, looking for a sweater.

Yeseniq Mejia, 30, who is seven months pregnant, lives in one of the larger tents at Benito Juarez. She made the grueling journey from San Pedro Sula, where the first caravan started in Honduras, with her two sons and husband.

Mejia was trying to decide whether to stay in Mexico or apply for asylum in the United States. She says she was worried about being separated from her children.

“They could even keep my baby,” Mejia said says, clutching her stomach.

The Trump administration ended its “zero tolerance” policy that separated migrant children from their families months ago but recently announced stricter requirements for applying for asylum.

While Mejia and the other migrants may be closer to the U.S. than they’ve ever been, it may take weeks, if not months, to be processed.

Tijuana’s mayor has called the migrants “an avalanche,” and the city is preparing for an influx that could last at least six months.

For the majority of migrants from the caravan, their next step is to apply for asylum at the San Ysidro Port of Entry. However, an official with Customs and Border Protection told NBC News that their ability to admit asylum seekers fluctuates on a daily basis.

One Honduran in line at the port of entry said border agents only let in nine people on Saturday.

“And then CBP told everyone to leave,” said the man, who did not want to give his name.

“We’ll come back tomorrow,” he added, standing next to his wife and holding his daughter.

For Mejia, the pregnant mother, there is a looming uncertainty.

“We could be here for weeks,” she said, folding a blanket she will use tonight as a pillow. “We’ll have to see how it all works out on our journey.”