Many of the nonprofits, corporations and religious groups watching over migrant children detained at the southwest border have been in this business for years — and they have a history of political connections, donating millions of dollars to Democrats and Republicans alike.

Now, as new federal policies greatly expand the number of migrants held in detention, it is also becoming clear that some of the players in this billion-dollar industry have particularly strong ties to the Trump administration.

The president’s education secretary provided funding to one of the groups. His defense secretary sat on the board of another. Mr. Trump’s own inauguration fund collected $500,000 from two private prison companies housing detained migrant families. And some of the contractors employ prominent Republican lobbyists with ties to Mr. Trump and his administration, including someone who once lobbied for his family business.

There is no indication that political favors or influence motivated any of the contracts, and the service providers have no apparent ties to the agency awarding most of the contracts, the Department of Health and Human Services. Many of the groups had federal contracts to work with migrant children long before President Trump took office.