The United States law enforcement agents encountered more than 171,000 migrants at the U.S.-Mexico border in March, the highest number in 15 years, based on the preliminary data released by Customs and Border Protection (CBP).

Despite the current count, the administration's top officials and President Joe Biden have still refused to call the situation a crisis. The Washington Post reported that the March figures represent the highest monthly total since 2006.

CBP also reported having taken more than 18,800 unaccompanied minors last month, which is a 99 percent increase from February and a figure way above the previous one-month high in May 2019.

In May 2019, the highest month of arrests during that year's crisis stood at 11,861.

"These numbers suggest a new level of challenge for the administration as they look for a sensible border strategy, particularly given the rise in the number of families," Andrew Selee, president of the nonpartisan Migration Policy Institute, said as reported by The Post.

Selee added that the administration is facing a set of hard options for trying to manage the flow in a way consistent with their aim of humanitarian treatment and yet discourages people from crossing the border.

Biden has downplayed the numbers of migrants crossing during his first news conference last week. The President went on to say that nothing has changed, adding that there is a significant increase in the number of people coming to the border during the winter months. He claimed that the current situation happens every year.

The Sun reported that the March figures also showed a 178 percent increase in the number of migrant families caught at the border than last month.

The total includes about 19,000 unaccompanied migrant children and 53,000 family members traveling together, while single adults accounted for about 99,000 of the total number.

A top U.S. border official said he expects more than a million migrants to arrive at the U.S.-Mexico border this year.

"We're already starting to see some higher days of 6,000-plus apprehensions," Raul Ortiz, deputy chief of the U.S. Border Patrol, said on Tuesday.

RELATED ARTICLE: Biden "Limits" Sharing of Info About Migrant Surge, Officials Claim 

Shelters for Migrants

U.S. officials have been struggling in recent weeks to open emergency shelters, including sites at convention centers in Dallas and San Diego.

Many unaccompanied teenagers and children were held in crowded conditions for far longer than what the law allows while waiting for bed space to open at emergency shelters managed by the Department of Health and Human Services.

CBP announced on Friday said they intend to open a new 90,000-square-foot tent facility near Eagle Pass, Texas. A similar site is also under consideration in Arizona.

Many migrants from the Central American countries attributed their border crossing to physical threats and poor economic conditions in their home countries.

White House Press Secretary Jen Psaki said they are not naive about the challenges. But they are focusing on solutions and actions to help unaccompanied minors at the border, Daily Mail reported.

Central American and Mexican migrants have accounted for the bulk of arrivals at the southern border in recent months. Biden said the administration is working to place the children with legal and educational services while being detained. 

His administration has continued to impose the Title 42 public-health order set by former President Donald Trump to quickly send most adult migrants to Mexico. 

READ MORE: Texas Gov. Abbott Places Troops in Borders Amid Immigration Crisis

WATCH: Migrant Crossings Rise Along U.S.-Mexico Border - From Associated Press