Two millionaire fugitives from Ecuador, whose family poured hundreds of thousands of dollars into American political campaigns as they fought to stay in the United States, were arrested last week in Miami by immigration authorities, officials said.

Roberto and William Isaías, 74 and 75, were taken on Wednesday to a detention facility where undocumented immigrants are held pending deportation, according to the federal Immigration and Customs Enforcement agency.

It was not immediately clear what prompted the authorities to make the arrests, but ICE’s statement said the brothers were “unlawfully present” in the United States.

The Isaías brothers, bankers vilified in Ecuador for increasing their wealth in the late 1990s just as their bank collapsed — wiping out tens of thousands of customers’ savings — were convicted of embezzlement by a court there in 2012. They were sentenced to prison terms in absentia, having arrived in South Florida almost a decade earlier.