EXPLAINER: Is the US border with Mexico in crisis?
Department of Homeland Security officers wait for the arrival of migrant children and teenagers from the southern border of the United States at the site of a temporary holding facility that opened Sunday, March 14, 2021 south of Midland, Texas. (Eli Hartman/Odessa American via AP)

Department of Homeland Security officers wait for the arrival of migrant children and teenagers from the southern border of the United States at the site of a temporary holding facility that opened Sunday, March 14, 2021 south of Midland, Texas. (Eli Hartman/Odessa American via AP)

Mar. 15, 2021 04:11 AM EDT
Migrant children are seen with adults as they wait in line to get a COVID-19 test before given travel instructions at a bus station, Wednesday, March 17, 2021, in Brownsville, Texas. A surge of migrants on the Southwest border has the Biden administration on the defensive. The head of Homeland Security acknowledged the severity of the problem Tuesday but insisted it's under control and said he won't revive a Trump-era practice of immediately expelling teens and children. An official says U.S. authorities encountered nearly double the number children traveling alone across the Mexican border in one day this week than on an average day last month. (AP Photo/Julio Cortez)

Migrant children are seen with adults as they wait in line to get a COVID-19 test before given travel instructions at a bus station, Wednesday, March 17, 2021, in Brownsville, Texas. A surge of migrants on the Southwest border has the Biden administration on the defensive. The head of Homeland Security acknowledged the severity of the problem Tuesday but insisted it's under control and said he won't revive a Trump-era practice of immediately expelling teens and children. An official says U.S. authorities encountered nearly double the number children traveling alone across the Mexican border in one day this week than on an average day last month. (AP Photo/Julio Cortez)

Mar. 17, 2021 05:49 PM EDT
Fifteen-month-old Matias Marin sits on the lap of his mother Naciel Marin, 23, of Nicaragua, as they wait for travel instructions to Wisconsin at a bus station in Brownsville, Texas, Wednesday, March 17, 2021. The Marin family left their native Nicaragua a month and half ago to seek asylum in the U.S. During their trek, Matias has become ill with a cold that his mother said still lingers. A surge of migrants on the Southwest border has the Biden administration on the defensive. The head of Homeland Security acknowledged the severity of the problem Tuesday but insisted it's under control and said he won't revive a Trump-era practice of immediately expelling teens and children. (AP Photo/Julio Cortez)

Fifteen-month-old Matias Marin sits on the lap of his mother Naciel Marin, 23, of Nicaragua, as they wait for travel instructions to Wisconsin at a bus station in Brownsville, Texas, Wednesday, March 17, 2021. The Marin family left their native Nicaragua a month and half ago to seek asylum in the U.S. During their trek, Matias has become ill with a cold that his mother said still lingers. A surge of migrants on the Southwest border has the Biden administration on the defensive. The head of Homeland Security acknowledged the severity of the problem Tuesday but insisted it's under control and said he won't revive a Trump-era practice of immediately expelling teens and children. (AP Photo/Julio Cortez)

Mar. 17, 2021 05:47 PM EDT
Larissa Bautista Hernandez, 2, second from left, a migrant from Honduras, is carried by her mother, Irma Hernandez, left, as her father, Jose Frankis Bautista, right, heads into a taxi cab at a bus station, Wednesday, March 17, 2021, in Brownsville, Texas. The family is seeking asylum from the U.S. and is getting help from Team Brownsville, a humanitarian group, to reach their final destination with Bautista's brother in South Carolina. A surge of migrants on the Southwest border has the Biden administration on the defensive. The head of Homeland Security acknowledged the severity of the problem Tuesday but insisted it's under control and said he won't revive a Trump-era practice of immediately expelling teens and children. (AP Photo/Julio Cortez)

Larissa Bautista Hernandez, 2, second from left, a migrant from Honduras, is carried by her mother, Irma Hernandez, left, as her father, Jose Frankis Bautista, right, heads into a taxi cab at a bus station, Wednesday, March 17, 2021, in Brownsville, Texas. The family is seeking asylum from the U.S. and is getting help from Team Brownsville, a humanitarian group, to reach their final destination with Bautista's brother in South Carolina. A surge of migrants on the Southwest border has the Biden administration on the defensive. The head of Homeland Security acknowledged the severity of the problem Tuesday but insisted it's under control and said he won't revive a Trump-era practice of immediately expelling teens and children. (AP Photo/Julio Cortez)

Mar. 17, 2021 05:50 PM EDT
FILE - In this March 14, 2021, file photo, migrant children and teenagers are processed after entering the site of a temporary holding facility south of Midland, Texas. Migration flows to the U.S. from Mexico are surging for the third time in seven years under Republican and Democratic presidents — and for similar reasons. (Eli Hartman/Odessa American via AP, File)

FILE - In this March 14, 2021, file photo, migrant children and teenagers are processed after entering the site of a temporary holding facility south of Midland, Texas. Migration flows to the U.S. from Mexico are surging for the third time in seven years under Republican and Democratic presidents — and for similar reasons. (Eli Hartman/Odessa American via AP, File)

Mar. 17, 2021 12:22 PM EDT