According to documents dated Monday, more than 3,200 unaccompanied migrant children were in customs and border protection custody. Of these, around 2,600 were waiting to be placed in accommodation suitable for minors, but just over 500 beds were available to accommodate them.

The latest data follows a trip by senior government officials to the US-Mexico border to assess the situation on the ground as the number of arrests increases, and indicates a rapidly growing trend for unaccompanied children to enter the US. Less than a week ago, around 1,700 children were in border protection custody.

As of Monday afternoon, President Joe Biden had not yet been informed by his top aides on the weekend trip that included a visit to a facility for unaccompanied migrant children in Carrizo Springs, Texas – the first facility for migrant children to open since Biden took office.

The officers were on investigation mode, said a familiar, and many took notes during their conversations. Biden is expected to be briefed in the coming days as aides spent part of the trip comparing notes and planning how the information would be presented to the president.

Among those who left was Susan Rice, former President Barack Obama’s national security adviser who now heads Biden’s Home Affairs Council. A source familiar with the visit told CNN that Rice was engaged during the visit and at times urged officials from the Department of Health and Human Services who operate the accommodation for unaccompanied migrants how to prepare for the surge respond and migrants process children more efficiently.

HHS told CNN in a statement Monday that the Office of Refugee Resettlement “is working aggressively with our interactors to ensure that unaccompanied migrant children are safely reunited with family members or other appropriate sponsors as quickly and safely as possible.”

“The number of unaccompanied children (UC) in our care is constantly changing,” the department said.

The growing number of unaccompanied children has raised alarm bells among officials looking for shelter for children during an ongoing pandemic that resulted in some places being unoccupied to meet health guidelines.

Monday’s data shows the ongoing bottleneck in the system as more children are detained than the U.S. government is willing to care for them. She also highlights the hurdles the Biden government faces when trying to take a more humanitarian approach to immigration while juggling the realities on the border.

The numbers are overwhelming. By comparison, at the height of the border crisis in 2019 – when overcrowded facilities and children slept on the floor – around 2,600 unaccompanied children were in border custody, a former CBP official told CNN.

A variety of reasons may be responsible for the sudden surge in children on the U.S.-Mexico border, including the dramatic aftermath of the pandemic in Latin America, where once expected economic growth rates have been decimated, the aftermath of two devastating hurricanes that hit the region and a perception of relaxed enforcement by the Biden government.

First Lady’s Chief of Staff Julissa Reynoso briefly discussed her trip to the US-Mexico border with a delegation of senior officials, including Minister of Rice and Homeland Security, Alejandro Mayorkas.

“We have spoken to a lot of the people involved, including children. We are trying to handle this in an orderly manner, but taking into account the human cost here and given that we are talking about children, something we manage,” Reynoso said Monday to reporters.

The group flew from Washington on a military plane and made their first stop at the CBP tent complex in Donna, Texas, in the Rio Grande Valley, where undocumented migrants were processed. From there, the group flew north along the border to Laredo, where they landed and drove to the facility that housed children in Carrizo Springs. The trip lasted most of the Saturday.

At the two locations, officers spoke to some of those in charge, some of the simple CBP and HHS officers working there, and some of the migrants being held at the facilities, including some of the children. Some of the officers on the trip speak Spanish and were able to communicate directly with the detained migrants.

On Friday, the Biden administration announced facilities caring for immigrant children that they can open up to pre-Covid-19 levels, recognizing “exceptional circumstances,” according to a memo received from CNN. After Border Patrol’s detention, unaccompanied children must be returned within 72 hours to the Department of Health and Human Services charged with caring for migrant children, unless exceptional circumstances exist.

Once treatment is complete, the case managers will work to place children with a sponsor such as a parent or relative in the United States. However, due to the coronavirus pandemic and the precautionary measures to avoid the spread of Covid-19, the department was only able to use just over half of the beds for children.

CNN reported last week that the average time at Border Patrol facilities not designed to accommodate children was 77 hours, longer than the 72 hours allowed under US law.

This trend seems to be continuing. According to records, more than 1,300 children had been detained for more than 72 hours. The majority of the children are 13 years and older.

This story has been updated with additional reports.

CNN’s Kevin Liptak contributed to this report.