A former Miami congressman who signed a $50 million consulting contract with Venezuela’s socialist government was arrested Monday in connection with an ongoing federal criminal investigation, law enforcement officials told The Associated Press.

David Rivera, a Republican who served from 2011 to 2013, was arrested at Atlanta’s airport, said Marlene Rodriguez, a spokesperson for the U.S. Attorney’s Office in Miami. She said Rivera was indicted by a Miami grand jury last month, but that document remains sealed and she could not discuss the charges.

Pressure has been building on Rivera for more than two years after it emerged that he received the massive contract from a U.S. affiliate of Venezuela’s state-owned oil company as President Nicolas Maduro was trying to curry favor with the White House in the early days of the Trump administration.