WASHINGTON—Venezuelan authorities rounded up U.S. oil executives held under house arrest in Caracas Wednesday night and moved them to a prison, the top U.S. envoy to Venezuela told reporters on Thursday.

The six employees of Houston-based Citgo Petroleum Corp were removed from their homes following a White House meeting between President Trump and Venezuela’s opposition leader, Juan Guaidó, on Wednesday.

Top U.S. envoy Elliott Abrams said the six Citgo employees, who have been detained since 2017 without trial, were believed to have been transferred to Helicoide prison in Caracas.

“We condemn this cruel and indefensible action and demand their long unjust detention come to an end and they be allowed to leave as well,” Mr. Abrams said.

The oil executives have been charged with corruption in Venezuela in connection to a planned $4 billion financing deal with U.S. and Dubai investment funds. Five are naturalized U.S. citizens, while the sixth is a permanent legal resident.