Haitian migrants gather by the thousands at Texas-Mexico border in hopes of entering U.S.

While the United States has dealt with migrant surges to its border, Department of Homeland Security Secretary Alejandro Mayorkas has described the mass migration seen over the past week to a U.S.-Mexico border entry location as unprecedented in its speed.

The vast majority of the migrants who have gathered at an international bridge in Del Rio, Texas, are Haitian. Haitians have been migrating to the U.S. in large numbers via South and Central America for several years, fleeing a country that has seen multiple earthquakes and endemic corruption and volatility.

The situation represents a humanitarian and logistical challenge for Joe Biden's administration, fresh off a large-scale withdrawal effortfrom Afghanistan and ongoing efforts to confronta pandemic that has killed over 670,000 Americans.

Conditions at camp

Migrants, mostly from Haiti, are shown Sept. 19 bathing near the banks of the Rio Grande in Del Rio, Texas, as seen from Ciudad Acuna, Mexico.

(John Moore/Getty Images)

Migrants wait it out near the bridge in hopes of being able to enter the U.S. or claim asylum, hanging their laundry to dry. While the surge to Del Rio has predominantly involved Haitians, there are also migrants from Cuba, Venezuelaand other countries.

(Go Nakamura/Reuters)

Unable to buy supplies or food in the U.S., migrants often cross back over the Rio Grande into Mexico to gather provisions.

(Fernando Llano/The Associated Press)

Haitian migrants receive food at a Mexican shelter in Ciudad Acuna, Coahuila state, on Sept. 21.

(Pedro Pardo/AFP/Getty Images)

Portable toilets, seen in the background, have been put up in response to the formation of the camp. As night falls, a boy plays with a stuffed animal.

(John Moore/Getty Images)

Enforcement a challenge

U.S. Border Patrol agents interact with Haitian immigrants on the bank of the Rio Grande in Del Rio, Texas, on Sept. 21. Previous images of agents on horseback who appeared to be using aggressive tactics while confronting the migrants have drawn sharp criticism from both human rights activists and the head of the U.S. Department of Homeland Security.

(John Moore/Getty Images)

Mexico has begun busing and flying Haitian migrants away from the U.S. border, authorities there have said. Haitian men are shown on Sept. 20 protesting to Mexican immigration officials after being detained in Ciudad Acuna, Coahuila state.

(Paul Ratje/AFP/Getty Images)

The U.S. has warned migrants to not make the journey and has been co-ordinatingflights to return Haitians to Port-au-Prince, including on Sept. 21, as a Coast Guard airplane sits on the tarmac at Del Rio International Airport. Filippo Grandi, the head of the UN refugee agency, has warned that U.S. expulsions to a volatile country might violate international law.

(Marco Bello/Reuters)

An aerial view shows the migrants gathered underneath the Ciudad Acuna-Del Rio International Bridge, which connects the U.S. and Mexican border cities. Traffic has often been closed on the bridge in recent days for safety reasons.

(Pedro Pardo/AFP/Getty Images)