Hundreds of African migrants have been arrested in Texas after a “dramatic rise” in arrivals at the southern US border, according to patrol agents.
More from 500 people from African countries were detained near the frontier city of Del Rio in the past week, said US Customs and Border Protection (CBP), which warned of a “humanitarian crisis”.
Most were families from the Republic of the Congo, the Democratic Republic of the Congo, and Angola.
“The introduction of this new population places additional burdens on processing stations, to include language and cultural differences,” said Del Rio sector chief patrol agent Raul Ortiz.
The recent arrivals included a group of 116 migrants detained after arriving at the southern US border late on 30 May.
“This large group from Africa further demonstrates the complexity and severity of the border security and humanitarian crisis at our southwest border,” Mr Ortiz added.
At least 300 African migrants have also travelled on to San Antonio, Texas, about 150 miles from Del Rio, with hundreds more expected in the next few days.
San Antonio’s city government has opened two support centres for those travelling and is working with local charities to provide food and emergency shelter.
The city is “in desperate need” of French-speaking volunteers, according to Jaleesa Irizarry, a reporter for local TV news station KENS 5.
Speakers of Portuguese and Lingala, a Bantu language used across much of the Congo, are also needed to provide translation services.
It is not clear exactly what routes the African migrants are taking the reach the US.
But some have told NPR they flew from Nairobi, Kenya, to Brazil before heading north through Colombia and Central America on a journey that took several months.
More than 4.5 million people have been displaced by multiple conflicts in the Democratic Republic of the Congo, where the United Nations Refugee Agency says there is "one of the most complex and challenging humanitarian situations worldwide".
Refugees face months-long waits for asylum applications to be processed at the US border, with illegal crossings increasing after Donald Trump threatened the close the border with Mexico.
So far this year more than 33,000 people have been arrested in the Del Rio area after entering the country, more than double the figure for the whole of the last financial year.
About a fifth were migrants from Mexico, with the remaining 80 per cent originating from 38 other countries.