Vice President Kamala Harris has yet to visit the southern border, but a children's book she wrote is waiting for unaccompanied young migrants who are being welcomed into the U.S.

According to New York Post, migrant children from the U.S.-Mexico border transferred to a new shelter in Long Beach, California will be given a copy of Harris' 2019 children's book, "Superheroes are Everywhere," as part of their welcome kits.

In the children's book, Kamala Harris says that "whenever there's trouble, superheroes show up just in time."

The New York Post has shown a picture of the said children's book placed on top of a cot together with a bag and some basic supplies at the Long Beach Convention & Entertainment Center.

The Long Beach Convention & Entertainment Center opened on Thursday as a new temporary facility for unaccompanied migrant children.

With the continued influx of migrants at the U.S.-Mexico border, the convention center will house up to 1,000 migrant children. The first 150 arrived at the center on Thursday.

Since President Joe Biden has tapped Kamala Harris to lead diplomatic efforts to address the rising number of migrants coming to the country last month, the vice president has yet to visit the southern border.

Kamala Harris earlier said that she had been asked to address the root causes of illegal migration and that Homeland Security Secretary Alejandro Mayorkas was the one in charge of the border crisis.

She also said that she will be visiting Guatemala and Mexico but will not go to the southern border to address the mass migration.

On Friday, the vice president decided to spend time at the Canadian border in New Hampshire, where she was greeted by protesters, who urged her to visit the U.S.-Mexico border as Biden's migration czar.

Kamala Harris was in New Hampshire to promote the president's $2 trillion infrastructure proposal.

"Vice President Kamala Harris would serve our nation better by tackling the crisis at our southern border instead of campaigning with Maggie Hassan near our northern border," New Hampshire GOP Chairman Stephen Stepanek said as reported by Breitbart News.

When the vice president was asked Friday about when she might visit the southern border, she ignored the question.

RELATED ARTICLE: Kamala Harris Purposely Avoiding a Visit to U.S.-Mexico Border, Border Patrol Union Chief Says

Kamala Harris on Border Crisis

Kamala Harris said the root causes of migration must be addressed. The vice president is currently in talks with Northern Triangle countries, which include Guatemala, El Salvador, and Honduras, Fox News reported.

In a roundtable on the Northern Triangle, Harris told participants that most people do not want to leave home. She cited reasons why migrants flee from their home countries, such as extreme climate that brings storms and drought, damaging a region where agriculture is an important basis for their economy.

"We're looking at what's happening in terms of food scarcity as a result of that and in fact, incredible food insecurity, which we used to call hunger food insecurity," Harris noted.

Harris added that extreme poverty, corruption, and violence are also among the reasons why migrants are fleeing their homes for the U.S.

"Again, we're looking at the issue of climate resiliency and then the concern about a lack of economic opportunity," Harris noted.

According to Biden administration officials, about 28 percent of migrants expelled from the U.S. in March had been ousted before, compared with a seven percent pre-pandemic recidivism rate in the 12-month period that ended in September 2019.

Families and children traveling alone accounted for more than 40 percent of all encounters in March, an increase of 13 percent three months earlier, Associated Press reported.

In March, border officials encountered 18,890 unaccompanied children, well above previous highs of 11,475 in May 2019 and 10,620 in June 2014, as reported by the Border Patrol.

Biden has exempted unaccompanied migrant children from pandemic-related expulsions, which allowed the minors to remain in the country to pursue asylum. Nearly 60 percent of families arriving at the southern border were allowed to stay in the U.S. last February. 

Mayorkas earlier attributed the rise to Mexico's inability to take back the families the U.S. is seeking to expel under an authority enacted during the coronavirus pandemic. Biden has kept a Trump-era policy that uses the COVID-19 pandemic to expel migrants.

READ MORE: Republican Senator Says Border Crisis Could Be Solved if Trump Immigration Policies Reinstated

WATCH: VP Kamala Harris Taking the Lead on Immigration - From ABC News